Secret communications of co-eds, possibly (5)
I believe the answer is:
codes
'secret communications' is the definition.
(I've seen this in another clue)
'co-eds possibly' is the wordplay.
'possibly' is an anagram indicator.
'eds' is an anagram of 'des'.
'co'+'des'='CODES'
'of' acts as a link.
(Other definitions for codes that I've seen before include "Symbolic systems" , "Lots of laws" , "morals" , "Ciphers" , "Word systems devised to create secrecy" .)