Fast and loose, by the sound of it? (8)
I believe the answer is:
rattling
This clue is a double definition.
'fast' is the first definition.
(eg rattling through something)
'loose by the sound of it?' is the second definition.
(having a loose, rattling sound)
'and' acts as a link.
(Other definitions for rattling that I've seen before include "Noisily shaking (as in good yarn)" , "Travelling at great speed" , "Smart" , "indication of loose parts?" , "Making short hard sounds" .)