Spike's a penniless western gunfighter (3)
I believe the answer is:
ear
'spike's' is the definition.
(spike is another term for an ear of grain)
'a penniless western gunfighter' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
(Other definitions for ear that I've seen before include "Seed container" , "Musical appreciation" , "Hearing aid?" , "Sense organ" , "Fruiting head of corn" .)