Mentally defeat some tipsy characters (5)
I believe the answer is:
psych
'mentally defeat' is the definition.
'some tipsy characters' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'PSYCH' is hidden within 'tipsy characters'.
(Other definitions for psych that I've seen before include "Intimidate someone by making him feel uneasy" , "To subject to mind games" , "Mind doctor (colloquial abbreviation)" , "Stimulate" .)