Unproductive time over for group of soldiers (5)
I believe the answer is:
troop
'group of soldiers' is the definition.
(I've seen this before)
'unproductive time over' is the wordplay.
'unproductive' becomes 'poor' (synonyms).
'time' becomes 't' (abbreviation).
'over' shows that the letters should be reversed in order.
'poor'+'t'='poort'
'poort' in reverse letter order is 'TROOP'.
'for' acts as a link.
(Other definitions for troop that I've seen before include "Cavalry unit commanded by a captain" , "Squad" , "Gang" , "herd" , "A company, unit" .)