Song he composed with firm bass from this person? (10)
I believe the answer is:
fishmonger
'bass from this person?' is the definition.
'fishmonger' can be an answer for 'person?' (fishmonger is a kind of person). I am not certain of the 'bass from this' bit.
'song he composed with firm' is the wordplay.
'composed with' indicates an anagram.
'song'+'he'='songhe'
'songhe' anagrammed with 'firm' gives 'FISHMONGER'.
Can you help me to learn more?
(Other definitions for fishmonger that I've seen before include "Shop" , "Seller of salmon, cod, etc" , "Shopkeeper" .)