Improve wayward children with no heart (6)
I believe the answer is:
enrich
'improve' is the definition.
(enriching is a kind of improving)
'wayward children with no heart' is the wordplay.
'wayward' indicates an anagram.
'with no heart' means to remove the middle letters.
'children' with its centre removed is 'chiren'.
'chiren' is an anagram of 'ENRICH'.
(Other definitions for enrich that I've seen before include "Give money" , "Add nutrients to" , "Make wealthy or improve the quality" , "Aggrandize" , "Grace" .)