Go limp, with nothing for starch (4)
I believe the answer is:
sago
'for starch' is the definition.
(sago is a kind of starch)
'go limp with nothing' is the wordplay.
'go limp' becomes 'sag' (I've seen this in another clue).
'with' is a charade indicator (letters next to each other).
'nothing' becomes 'O' (looks like zero - 0).
'sag'+'o'='SAGO'
(Other definitions for sago that I've seen before include "Edible palm starch" , "Starchy cereal used in puddings" , "Starchy pudding cereal" , "Starchy foodstuff" , "Powdery starch used in cooking" .)