Turn up gas ring for pudding (4)
I believe the answer is:
sago
'pudding' is the definition.
(I've seen this before)
'turn up gas ring' is the wordplay.
'turn up' is a reversal indicator.
'ring' becomes 'o'.
'gas' in reverse letter order is 'sag'.
'sag'+'o'='SAGO'
'for' is the link.
(Other definitions for sago that I've seen before include "Powdery starch used in cooking" , "Starchy food as white pudding" , "Starchy foodstuff" , "Powdery starchy food" , "Cereal, used in pudding" .)