Go down and turn up the gas (3)
I believe the answer is:
sag
'go down' is the definition.
(thesaurus)
'turn up the gas' is the wordplay.
'turn up' is a reversal indicator.
'gas' backwards is 'SAG'.
'and' is the link.
(Other definitions for sag that I've seen before include "Sinking" , "Drop" , "fall" , "Fail to retain interest" , "Subsidence" .)