Person grilling odd sandwiches is not out to lunch (10)
I believe the answer is:
questioner
'person grilling' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'odd sandwiches is not out to lunch' is the wordplay.
'odd' becomes 'queer' (I've seen this in another clue).
'sandwiches' is an insertion indicator (inserted letters are sandwiched in).
'out to lunch' indicates anagramming the letters (out to lunch can mean mad).
'is'+'not'='isnot'
'isnot' is an anagram of 'stion'.
'queer' placed around 'stion' is 'QUESTIONER'.
Can you help me to learn more?
(Other definitions for questioner that I've seen before include "Person expressing doubts" , "examiner" , "Interrogator" .)