Unproductive time up for body of soldiers (5)
I believe the answer is:
troop
'body of soldiers' is the definition.
(I've seen this before)
'unproductive time up' is the wordplay.
'unproductive' becomes 'poor' (synonyms).
'time' becomes 't' (abbreviation).
'up' is a reversal indicator (in down clue: letters go upwards).
'poor'+'t'='poort'
'poort' in reverse letter order is 'TROOP'.
'for' is the link.
(Other definitions for troop that I've seen before include "Group of people or animals" , "Flock; Scout group" , "Group of, eg, monkeys" , "A company of people, soldiers or scouts" , "Group of kangaroos" .)