Drop a brick into modest drink (6)
I believe the answer is:
sherry
'drink' is the definition.
(I know that Sherry is a drink)
'drop a brick into modest' is the wordplay.
'drop a brick' becomes 'err' (I've seen this in another clue).
'into' indicates putting letters inside.
'modest' becomes 'shy'.
'err' going within 'shy' is 'SHERRY'.
(Other definitions for sherry that I've seen before include "Wine from Spain's Jerez region, drunk as an aperitif" , "Alcoholic appetiser associated with Jerez" , "Alcoholic drink" , "Wine from the Jerez region of Spain" , "Preprandial drink" .)