The 1960's have been remembered as a tumultuous decade, with music that reflected the protest and disorder as youth rebelled against the old order. But despite that common notion, I could probably count on both hands the songs of the 1960s that directly address the social and political turmoil of the time, and I would only need one hand to count the songs that had something to say.
I would include "Slip Kid" on my list of songs on this list, except it isn't from the 1960's, being released in 1975, and isn't precisely about the social upheaval of the 1960's, although it was obviously inspired in part by them. But the song is actually part of Pete Townsend's unrecorded concept album, Lifehouse. You can actually go and read the internal and external story behind Lifehouse, on here, or in other parts of the internet, and you will probably end up more confused. The brief summary is that Lifehouse was a too-ambitious project to tell a science-fiction story that ended up with several great songs, such as Behind Blue Eyes, Won't Get Fooled Again, and Baba O'Riley, that are rock staples, but which are often listened to outside of the context.
And so it is with "Slip Kid", which can be listened to as a revolutionary anthem by its own, without knowing about the larger story it is part of.
Great music, especially rock music, can carry a message without being propaganda. This song is evocative, without being clear what it is actually about. Recently, thinking about the start of the current social movement in Chile, I realized that the opening lines of the song "I've got my clipboard, my textbooks, take me to the station, I'm off to the civil war...I'm a soldier at 13" seem to be literally written about the campaign of fare evasion started by middle school students that launched that movement. And great music can do that: suddenly seem immediately meaningful, far from the context it was written and performed under.
If you listen to the song further, the song introduces another character: an older man, who himself is leaving in a hurry to join the civil war. The two characters join in recriminations, but from the song, it is not clear whether they are fighting on the same side or against each other. That, like so much else in the song and in the Who's work of the period, seems to be up to the listener to decide.
If there is one thing I would deduce about the song, from both the music and the lyrics, is the difference between the exhilaration of fighting and rebelling, ("run until my feet are raw", "I left my door ajar"), and the downside when they realize "there is no easy way to be free". The song's shift between excitement and introspection is why it is a great song about revolution, even though the specifics of the situation are not necessarily clear.