Old soldiers find small signs (5)
I believe the answer is:
omens
'signs' is the definition.
(I know this)
'old soldiers find small' is the wordplay.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'soldiers' becomes 'men' (men can mean a group of soldiers).
'find' is a charade indicator (letters next to each other).
'small' becomes 's' (abbreviation - e.g. clothes size).
'o'+'men'+'s'='OMENS'
(Other definitions for omens that I've seen before include "Auguries" , "Prophetic signs of good or evil" , "Harbingers, portents" , "Signs or warnings for the future" , "Signs of things to come" .)