Collective held back by cadet in Ukraine (6)
I believe the answer is:
united
'collective' is the definition.
(associated in meaning)
'held back by cadet in ukraine' is the wordplay.
'back by' is a reversal indicator.
'held' indicates the answer is hidden within the clue.
'detinu' can be found hidden inside 'cadet in ukraine'.
'detinu' in reverse letter order is 'UNITED'.
(Other definitions for united that I've seen before include "Amalgamated" , "Untied (anag.)" , "Of like mind" , "Football team" , "Whole" .)