Drink, being hesitant to admit mistake (6)
I believe the answer is:
sherry
'drink' is the definition.
(I know that Sherry is a drink)
'hesitant to admit mistake' is the wordplay.
'hesitant' becomes 'shy' (I can't justify this - if you can you should believe this answer much more).
'to admit' means one lot of letters goes inside another.
'mistake' becomes 'err' (to err is to make a mistake or blunder).
'shy' placed around 'err' is 'SHERRY'.
'being' acts as a link.
Can you help me to learn more?
(Other definitions for sherry that I've seen before include "Christmas drink?" , "booze" , "Pre-dinner aperitif as from Jerez" , "Alcoholic appetiser associated with Jerez" , "Fortified wine as aperitif" .)