Inept sot struggling to go faster (4,2,2)
I believe the answer is:
step on it
'go faster' is the definition.
(I've seen this before)
'inept sot struggling' is the wordplay.
'struggling' indicates an anagram.
'inept'+'sot'='ineptsot'
'ineptsot' is an anagram of 'STEP ON IT'.
'to' is the link.
(Other definitions for step on it that I've seen before include "Go for speed" , "Hurry up, put foot down on pedal" , "Go faster - put foot down" , "to flatten an insect?" , "improve rate of advance" .)