Be likely to order a Christmas tree brought round (3,4)
I believe the answer is:
bid fair
'be likely' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'order a christmas tree brought round' is the wordplay.
'order' becomes 'bid' (I've seen this in another clue).
'christmas tree' becomes 'fir' (firs are often used as Christmas trees).
'brought round' means one lot of letters goes inside another.
'a' going inside 'fir' is 'fair'.
'bid'+'fair'='BID FAIR'
'to' acts as a link.
Can you help me to learn more?
(Another definition for bid fair that I've seen is " shows promise".)