Yours truly playing clarinet in commercial (10)
I believe the answer is:
mercantile
'commercial' is the definition.
(similar in meaning)
'yours truly playing clarinet in' is the wordplay.
'yours truly' becomes 'me'.
'playing' indicates an anagram.
'in' is an insertion indicator.
'clarinet' with letters rearranged gives 'ercantil'.
'me' going around 'ercantil' is 'MERCANTILE'.
(Other definitions for mercantile that I've seen before include "Relating to trade or commerce" , "concerning trade" , "Relating to (overseas) trade" , "related to business" , "Dealing with trade" .)