Many beginning to steal hearts (6)
I believe the answer is:
scores
'many' is the definition.
(thesaurus)
'beginning to steal hearts' is the wordplay.
'beginning to' says to take the initial letters.
'hearts' becomes 'cores' ('core' can be a synonym of 'heart').
The first letter of 'steal' is 's'.
's'+'cores'='SCORES'
(Other definitions for scores that I've seen before include "Scratches" , "Written forms of a musical composition" , "Written forms of musical compositions" , "Musical compositions in written form" , "Puts ball in the net" .)