Bit of excess gas, sir, turned up after favourite part of massage (10)
I believe the answer is:
petrissage
'massage' is the definition.
(I've seen this before)
'bit of excess gas sir turned up after favourite' is the wordplay.
'bit of' says to take the initial letters.
'turned up' is a reversal indicator.
'after' is a charade indicator (letters next to each other).
'favourite' becomes 'pet' (synonyms).
The initial letter of 'excess' is 'e'.
'e'+'gas'+'sir'='egassir'
'egassir' written backwards gives 'rissage'.
'rissage' after 'pet' is 'PETRISSAGE'.
'part of' is the link.
(Another definition for petrissage that I've seen is " massage".)