At the volley of fire, there's a sudden increase in speed (5)
I believe the answer is:
burst
'fire there's a sudden increase in speed' is the definition.
I can't judge whether this definition defines the answer.
'at the volley' is the wordplay.
'at' means one lot of letters go next to another.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'volley' becomes 'burs' (I can't justify this - if you can you should believe this answer much more).
't' put after 'burs' is 'BURST'.
'of' is the link.
Can you help me to learn more?
(Other definitions for burst that I've seen before include "Explode (as 1 acrosses do)" , "Blow up" , "Fit" , "sudden break" , "Explode, erupt" .)