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' indicates taking the first letters.
'turned up' is a reversal indicator.
'after' means one lot of letters go next to another.
'favourite' becomes 'pet' (synonyms).
The initial letter of 'excess' is 'e'.
'e'+'gas'+'sir'='egassir'
'egassir' backwards is 'rissage'.
'rissage' after 'pet' is 'PETRISSAGE'.
'part of' is the link.
(Another definition for petrissage that I've seen is " massage".)