Influence of heartless figure pierced by nail (7)
I believe the answer is:
impinge
'influence' is the definition.
(impinge can mean to affect or influence)
'heartless figure pierced by nail' is the wordplay.
I cannot really see how this works, but
'nail' could be 'pin' (I've seen this before) and 'pin' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for impinge that I've seen before include "Encroach on the pig in me" , "Make an impact, encroach" , "Trespass (upon)" , "Make an impact, or have bearing on" , "Encroach (upon)" .)