Lots of dogs failing to start (6)
I believe the answer is:
oodles
'lots of' is the definition.
(I've seen this before)
'dogs failing to start' is the wordplay.
'dogs' becomes 'poodles' (poodle is a kind of dog).
'failing to start' means to remove the first letter.
'poodles' with its first letter taken away is 'OODLES'.
(Other definitions for oodles that I've seen before include "Plenty" , "A lot" , "masses" , "Tons, scads" , "Lashings, loads" .)