Musician playing in recitals outside front of theatre repeatedly (12)
I believe the answer is:
clarinettist
'musician' is the definition.
(clarinettist is a kind of musician)
'playing in recitals outside front of theatre repeatedly' is the wordplay.
'playing' is an anagram indicator.
'outside' indicates putting letters inside.
'front of' indicates taking the first letters.
'repeatedly' says to double the letters.
The initial letter of 'theatre' is 't'.
'in'+'recitals'='inrecitals'
'inrecitals' is an anagram of 'clarineist'.
't' doubled is 'tt'.
'clarineist' placed around 'tt' is 'CLARINETTIST'.
(Other definitions for clarinettist that I've seen before include "Musician, like Benny Goodman, say" , "Cats in litter (anag) -- woodwind player" .)