Old lad was far out creating this dish! (7,5)
I believe the answer is:
waldorf salad
'this dish' is the definition.
(Waldorf salad is an example)
'old lad was far out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'old'+'lad'+'was'+'far'='oldladwasfar'
'oldladwasfar' with letters rearranged gives 'WALDORF SALAD'.
'creating' is the link.
(Other definitions for waldorf salad that I've seen before include "Mix of apples, walnuts, celery, etc" , "Apples, celery, walnuts and mayo" , "eats" , "Vegetarian dish of celery, apples, walnuts and mayonnaise" .)