Christ, this kind of dubious thirty years ago, now just embarrassing, braggadocio on behalf of an organisation you dropped out of decades ago is almost funny.
Cliff, whatever his other merits, contributed pretty much nothing of lasting interest to Marxist understandings of various forms of oppression other than class. Exactly the same can be said of Ted Grant (and thank Christ he didn't produce a book on "the woman question" to go alongside Cliff's embarrassing effort). In so far as there were any interesting theoretical contributions on these issues made in IS/SWP circles they were from other people.
Cliff himself veered all over the place. Largely it seems in response to short term party-building concerns. But as he was the central leader of the SWP, the varying angles he took are of interest not on their own merits but because they indicate the lack of an IS/SWP "tradition" or orthodoxy up until the end of the fights of the eighties. At that point the orthodoxy settled and remained unchanged up until the recent interest in Vogel.