Milk pudding needs gas ring cooking (4)
I believe the answer is:
sago
'milk pudding' is the definition.
(I've seen this before)
'gas ring cooking' is the wordplay.
'ring' becomes 'O' (letter resembling a ring).
'cooking' is an anagram indicator (letters cooked up into a new form).
'gas'+'o'='gaso'
'gaso' with letters rearranged gives 'SAGO'.
'needs' acts as a link.
(Other definitions for sago that I've seen before include "Starchy food as white pudding" , "Powdery starchy food" , "Cereal, used in pudding" , "Starchy cereal used in puddings" , "dessert?" .)