Ten meagre changes to harmony (9)
I believe the answer is:
agreement
'harmony' is the definition.
(agreement is a kind of harmony)
'ten meagre changes' is the wordplay.
'changes' is an anagram indicator.
'ten'+'meagre'='tenmeagre'
'tenmeagre' anagrammed gives 'AGREEMENT'.
'to' acts as a link.
(Other definitions for agreement that I've seen before include "Harmony, concurrence" , "Harmony or treaty" , "Compact, accord" , "Union < matching" , "Accord, contract" .)