Workers' groups put together gear for Kirov, perhaps (4)
I believe the answer is:
tutu
'gear for kirov perhaps' is the definition.
(as in the Kirov Ballet)
'workers' groups put together' is the wordplay.
'workers'' becomes 'tu' (abbreviation for trade union).
'groups put together' becomes 'tu' (I am not sure about this - if you are sure you should believe this answer much more).
'tu'+'tu'='TUTU'
(Other definitions for tutu that I've seen before include "Female ballet costume" , "Ballet dancer's short skirt" , "Archbishop Desmond" , "Ballet dancer's costume" , "A ballerina's short skirt" .)