Snag possibly involving student in loose language (5)
I believe the answer is:
slang
'loose language' is the definition.
(I've seen this in another clue)
'snag possibly involving student' is the wordplay.
'possibly' indicates an anagram.
'involving' means one lot of letters goes inside another.
'student' becomes 'l' (as in L-plates for learner drivers).
'snag' anagrammed gives 'sang'.
'sang' going around 'l' is 'SLANG'.
'in' is the link.
(Other definitions for slang that I've seen before include "Vulgar parlance" , "Unconventional language" , "common language" , "Vernacular" , "Colloquial language" .)