Quick with the cash (5)
I believe the answer is:
ready
This clue is a double definition.
'quick' is the first definition.
(I know that quick can be written as ready)
'the cash' is the second definition.
(ready can informally refer to cash)
'with' is the link.
(Other definitions for ready that I've seen before include "At hand" , "game?" , "for immediate use" , "Prompt and adequate" , "Intelligent" .)