Chap swallows first of the riesling before some cheese (7)
I believe the answer is:
gruyere
'some cheese' is the definition.
(Gruyere is an example)
'chap swallows first of the riesling before' is the wordplay.
'chap' becomes 'guy'.
'swallows' means one lot of letters goes inside another.
'first of' suggests taking the first letters.
'before' becomes 'ere' (poetic term for 'before').
The initial letter of 'riesling' is 'r'.
'guy' going around 'r' is 'gruy'.
'gruy'+'ere'='GRUYERE'
(Other definitions for gruyere that I've seen before include "Whole-milk Swiss cheese" , "Swiss cheese with small holes" , "Firm pale cheese with holes" , "Tangy cheese" , "Hard yellow Swiss cheese" .)