Start off well — pint making you clumsy? (5)
I believe the answer is:
inept
'clumsy?' is the definition.
(I know that clumsy can be written as inept)
'start off well pint' is the wordplay.
'start off' means to remove the first letter (the start of the word is taken off).
'well' becomes 'fine' (similar in meaning).
'pint' becomes 'pt' (abbreviation).
'fine' with its initial letter taken away is 'ine'.
'ine'+'pt'='INEPT'
'making you' is the link.
(Other definitions for inept that I've seen before include "Incompetent and ineffectual" , "Incompetent or gauche" , "Hopeless; bungling" , "Awkward, showing no skill" , "Futile" .)