Once in the middle of kiss, hugged by imbecile (5)
I believe the answer is:
twixt
'once in the middle' is the definition.
(archaic word meaning 'in the middle')
'kiss hugged by imbecile' is the wordplay.
'kiss' becomes 'x'.
'hugged by' means one lot of letters goes inside another (I've seen this in other clues).
'imbecile' becomes 'twit'.
'x' placed inside 'twit' is 'TWIXT'.
'of' is the link.
(Other definitions for twixt that I've seen before include "dividing" , "Between (archaic)" .)