Female in army group is out of condition (5)
I believe the answer is:
unfit
'out of condition' is the definition.
(similar in meaning)
'female in army group' is the wordplay.
'female' becomes 'f' (abbreviation).
'in' is an insertion indicator.
'army group' becomes 'unit' (group of soldiers).
'f' placed inside 'unit' is 'UNFIT'.
'is' acts as a link.
(Other definitions for unfit that I've seen before include "Not in good physical shape (5)" , "Not prepared" , "Inapt" , "Not in good physical condition, or not suitable" , "not worthy" .)