Vacation time for a composer (5)
I believe the answer is:
holst
'for a composer' is the definition.
(Gustav Holst)
'vacation time' is the wordplay.
'vacation' becomes 'hols' (short for holidays).
'time' becomes 't' (abbreviation).
'hols'+'t'='HOLST'
(Other definitions for holst that I've seen before include "musical writer" , "Planets Suite composer" , "He scored" , "Composer of The Planets, d. 1934" , "Gustav --, English composer" .)