A few always involved in the Spanish uprising (7)
I believe the answer is:
several
'a few' is the definition.
(I've seen this before)
'always involved in the spanish uprising' is the wordplay.
'always' becomes 'ever' (synonyms).
'involved in' is an insertion indicator.
'the spanish' becomes 'las' ('the' in Spanish).
'uprising' shows that the letters should be reversed in order.
'las' written backwards gives 'sal'.
'ever' put into 'sal' is 'SEVERAL'.
(Other definitions for several that I've seen before include "quite a lot" , "More than one or two" , "Various, sundry" , "Some participants" , "A few; separate" .)