Figure of girl soldier seen on square (5)
I believe the answer is:
digit
'figure' is the definition.
(numerical figure)
'girl soldier seen on square' is the wordplay.
'girl' becomes 'Di' (short for Diane or Diana).
'soldier' becomes 'GI' (GI can mean a US soldier).
'seen on' is a charade indicator (letters next to each other).
'square' becomes 'T' (a T-Square is a technical drawing instrument).
'di'+'gi'+'t'='DIGIT'
'of' acts as a link.
(Other definitions for digit that I've seen before include "One in ten, say" , "one of several at hand" , "One's on hand" , "finger, perhaps" , "zero, one, two, three, four, five, six, seven, eight, or nine" .)