Understanding how to sing hit composition (7)
I believe the answer is:
insight
'understanding' is the definition.
(insight is a kind of understanding)
'to sing hit composition' is the wordplay.
'composition' is an anagram indicator.
'sing'+'hit'='singhit'
'singhit' anagrammed gives 'INSIGHT'.
'how' acts as a link.
(Other definitions for insight that I've seen before include "Penetrative quality" , "Intuitive understanding" , "percipience" , "Awareness" , "what psychoanalysts hope to gain" .)