Cry about small sign of life (5)
I believe the answer is:
pulse
'sign of life' is the definition.
(I've seen this before)
'cry about small' is the wordplay.
'cry' becomes 'pule' (puling is a kind of crying**).
'about' is an insertion indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'pule' going around 's' is 'PULSE'.
(Other definitions for pulse that I've seen before include "Beat or throb of heart" , "A vital sign turning" , "Musical beat; edible seeds" , "Lentil, bean, seeds" , "Vibration" .)