A study group made up of marines (7)
I believe the answer is:
seminar
'a study group' is the definition.
(I've seen this in another clue)
'up of marines' is the wordplay.
'up of' indicates an anagram (I've seen 'up' mean this (letters get chucked up)).
'marines' with letters rearranged gives 'SEMINAR'.
'made' is the link.
(Other definitions for seminar that I've seen before include "Tutorial group meeting" , "Meeting for study" , "Student discussion group - remains (anag)" , "Meeting for exchange of ideas" , "Short intensive study course for marines" .)