Overtime? Blast! (4)
I believe the answer is:
toot
'blast' is the definition.
(thesaurus)
'overtime?' is the wordplay.
I cannot quite see how this works, but
'overtime?' could be 'ot' (O and T are abbreviations for over and time) and 'ot' is found in the answer.
The remaining letters 'to' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for toot that I've seen before include "Blow a horn" , "Sound of a car horn" , "honk horn" , "Use horn" , "Short sound of horn" .)