Piano then fiddle I learnt as composer (10)
I believe the answer is:
palestrina
'composer' is the definition.
(Giovanni Pierluigi da Palestrina)
'piano then fiddle i learnt as' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'then' means one lot of letters go next to another.
'fiddle' is an anagram indicator.
'i'+'learnt'+'as'='ilearntas'
'ilearntas' anagrammed gives 'alestrina'.
'p'+'alestrina'='PALESTRINA'
(Other definitions for palestrina that I've seen before include "16th century Italian choral composer" , "He composed music" , "musician" , "Italian Renaissance composer" .)