Knight going out for small drink (6)
I believe the answer is:
noggin
'small drink' is the definition.
(I've seen this before)
'knight going out' is the wordplay.
'knight' becomes 'n' (chess).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'going' with letters rearranged gives 'oggin'.
'n'+'oggin'='NOGGIN'
'for' is the link.
(Other definitions for noggin that I've seen before include "Measure of alcohol, about a quarter pint" , "Small measure of spirits or slangy head" , "Gill usually" , "Human head -- small drink" , "Peg" .)