Start off well: pint makes 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'
'makes you' acts as a link.
(Other definitions for inept that I've seen before include "lacks skill" , "Incompetent or awkward" , "Hopelessly incapable" , "Silly - unskilled - unsuitable" , "Maladroit" .)