Grass one found in jungle? (5)
I believe the answer is:
maize
'grass' is the definition.
(thesaurus)
'one found in jungle?' is the wordplay.
'one' becomes 'i' (Roman numeral).
'found in' means one lot of letters goes inside another.
'jungle?' becomes 'maze' (I've seen this in other clues).
'i' placed within 'maze' is 'MAIZE'.
(Other definitions for maize that I've seen before include "Sweet corn" , "Source of oil" , "Corn-cob cereal" , "Tall cereal plant bearing grain on large pods" , "Source of sweetcorn" .)