Musical player regularly in charge (5)
I believe the answer is:
lyric
'musical' is the definition.
(thesaurus)
'player regularly in charge' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'in charge' becomes 'ic'.
The alternating letters of 'player' are 'lyr'.
'lyr'+'ic'='LYRIC'
(Other definitions for lyric that I've seen before include "Of poetry that expresses thoughts and feelings" , "Of poetry that expresses the poet's feelings" , "One barred from native country" , "Cyril (anag.)" , "Words to a song" .)