Enters tinsel to become leading star (7)
I believe the answer is:
enlists
'enters' is the definition.
(enlisting is a kind of entering)
'tinsel to become leading star' is the wordplay.
'to become' indicates an anagram.
'leading' says to take the initial letters.
The initial letter of 'star' is 's'.
'tinsel' anagrammed gives 'enlist'.
'enlist'+'s'='ENLISTS'
(Other definitions for enlists that I've seen before include "Recruits" , "gets involved" , "volunteers" , "Listens (anag.)" , "Signs up" .)