In spilling a pint, one's sweetheart is pretty useless! (5)
I believe the answer is:
inept
'useless' is the definition.
(I've seen this before)
'in spilling a pint one's sweetheart is pretty' is the wordplay.
I cannot really see how this works, but
'in' is present in the answer.
'pint' could be 'pt' (abbreviation) and 'pt' is found within the answer.
'sweetheart' could be 'e' (the middle letter or heart of 'sweet') and 'e' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for inept that I've seen before include "Cack-handed" , "Useless, awkward" , "Showing a lack of competence" , "Lousy" , "Unskilful or unsuitable" .)