Talent for finding underground bar for a quick drop (8)
I believe the answer is:
nosedive
'a quick drop' is the definition.
'talent for finding underground bar' is the wordplay.
'talent for finding' becomes 'nose' (as in 'a nose for a good deal').
'underground bar' becomes 'dive' (**).
'nose'+'dive'='NOSEDIVE'
'for' acts as a link.
(Other definitions for nosedive that I've seen before include "headlong plunge" , "fall precipitately" , "plummet" , "steep fall" , "(Make a) steep downward plunge" .)