Sweet gents maybe heading up north of Cork? (10)
I believe the answer is:
gobstopper
'sweet' is the definition.
(type of large sweet)
'gents maybe heading up north of cork?' is the wordplay.
'gents maybe' becomes 'bog' (the gents is a toilet or bog).
'heading up' is a reversal indicator (in a down clue, letters go up).
'north of' means one lot of letters go next to another (in a down clue, some letters go above others).
'cork?' becomes 'stopper' (cork is a kind of stopper).
'bog' written backwards gives 'gob'.
'gob'+'stopper'='GOBSTOPPER'
(Other definitions for gobstopper that I've seen before include "Large, hard spherical sweet" , "Large, hard sweet to suck" , "Hard round sweet" , "Big sweet" .)