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' says the letters should be written in reverse.
'gas' in reverse letter order is 'SAG'.
'and' acts as a link.
(Other definitions for sag that I've seen before include "Sinking" , "Drop" , "fall" , "Fail to retain interest" , "Subsidence" .)