Pea showing sign of life? (5)
I believe the answer is:
pulse
I believe this clue is a double definition.
'pea' is the first definition.
(thesaurus)
'sign of life?' is the second definition.
(a person's pulse)
'showing' is the link.
(Other definitions for pulse that I've seen before include "Heart-throb" , "Musical beat; edible seeds" , "Beat - lentil" , "Beat or throb of heart" , "flageolet?" .)