Nice, but would I be up to it? (7)
I believe the answer is:
amiable
'nice' is the definition.
(I've seen this in another clue)
'would i be up to it?' is the wordplay.
'would i' becomes 'ami' (I can't justify this - if you can you should give a lot more credence to this answer).
'be up to it?' becomes 'able' (up to it means able to do something).
'ami'+'able'='AMIABLE'
'but' is the link.
Can you help me to learn more?
(Other definitions for amiable that I've seen before include "Good-humoured" , "'Friendly, pleasant and good-tempered (7)'" , "Of sweet and friendly disposition" , "'Affable, genial (7)'" , "Friendly and good-natured (7)" .)