Skill I kindled in a boy, nothing less (7)
I believe the answer is:
ability
'skill' is the definition.
(thesaurus)
'i kindled in a boy nothing less' is the wordplay.
'kindled' becomes 'lit' ('lit' can be a synonym of 'kindled').
'in' is an insertion indicator.
'nothing' becomes 'o' (looks like zero - 0).
'less' is a deletion indicator.
'boy' with 'o' taken out is 'by'.
'i'+'lit'='ilit'
'a'+'by'='aby'
'ilit' inserted into 'aby' is 'ABILITY'.
(Other definitions for ability that I've seen before include "Skill, talent" , "Aptitude - competence" , "Capacity, competence" , "Aptitude - expertise" , "Proficiency" .)