Offer and pay for a case of red that's average (8)
I believe the answer is:
standard
'that's average' is the definition.
(similar in meaning)
'offer and pay for a case of red' is the wordplay.
'offer and pay for' becomes 'stand' (eg standing someone a drink).
'case of' suggests removing the centre (outsides of).
'red' with its middle removed is 'rd'.
'stand'+'a'+'rd'='STANDARD'
(Other definitions for standard that I've seen before include "Classic" , "Flag - norm" , "authority" , "Touchstone, benchmark 98)" , "Ordinary Level?" .)