Month round north is plenty (4)
I believe the answer is:
many
'is plenty' is the definition.
(I've seen this in another clue)
'month round north' is the wordplay.
'month' becomes 'may' (May is an example).
'round' indicates putting letters inside.
'north' becomes 'N' (abbreviation).
'may' going around 'n' is 'MANY'.
(Other definitions for many that I've seen before include "A lot of" , "multitude" , "Multitudinous" , "regarded as a large number" , "Numerous" .)