About due to finish, to spill a pint is useless (5)
I believe the answer is:
inept
'useless' is the definition.
(I've seen this in another clue)
'about due to finish to spill a pint' is the wordplay.
'about' means one lot of letters goes inside another.
'to finish' indicates one should take the final letters.
'to spill' is an anagram indicator (letters spilled or knocked around).
The last letter of 'due' is 'e'.
'pint' is an anagram of 'inpt'.
'e' put within 'inpt' is 'INEPT'.
'is' is the link.
(Other definitions for inept that I've seen before include "Hopeless; bungling" , "Foolish" , "Clumsy, bungling" , "Incompetent and ineffectual" , "Awkward, showing no skill" .)