Cook recipe with ground oats (5)
I believe the answer is:
roast
'cook' is the definition.
(roasting is a kind of cooking)
'recipe with ground oats' is the wordplay.
'recipe' becomes 'r' (abbreviation).
'with' means one lot of letters go next to another.
'ground' is an anagram indicator (grind the letters ).
'oats' anagrammed gives 'oast'.
'r'+'oast'='ROAST'
(Other definitions for roast that I've seen before include "Cooked like chestnuts tonight" , "Cooked meat; criticise" , "Cook with dry heat" , "Traditional Sunday lunch" , "Heat strongly - criticise excessively" .)