Seem likely to make a reasonable offer (3,4)
I believe the answer is:
bid fair
'seem likely to make a' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'reasonable offer' is the wordplay.
I cannot quite understand how this works, but
'reasonable' could be 'fair' (synonyms) and 'fair' is found in the answer.
'offer' could be 'bid' (bid is a kind of offer) and 'bid' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for bid fair that I've seen is " shows promise".)