Deal with a composer, by the sound of it (6)
I believe the answer is:
handle
'deal with' is the definition.
(synonyms)
'a composer by the sound of it' is the wordplay.
'a composer' becomes 'Handel' (George Frideric Handel).
'by the sound of it' shows a homophone (sound like).
'handel' is a homophone of 'HANDLE'.
(Other definitions for handle that I've seen before include "Deal with; name (colloq.)" , "Person's name (slang)" , "Part by which something is held" , "Knob" , "Part by which something is carried" .)