Quadrupedal start turn (4)
I believe the answer is:
rats
'quadrupedal start' is the definition.
Although both the answer and 'start' are verbs, they are not in the same form of the verb.
'turn' is the wordplay.
I cannot quite see how this works, but
'turn' could be 't' (abbreviation in Oxford Dictionary of Abbreviations) and 't' is found within the answer.
The remaining letters 'ras' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rats that I've seen before include "Tells" , "Oh no" , "Damn" , "Annoyed expression" , "First word of 'The 21 19'" .)