Learner in a sad mess with the food (5)
I believe the answer is:
salad
'the food' is the definition.
(salad is a kind of food)
'learner in a sad mess' is the wordplay.
'learner' becomes 'l'.
'in' indicates putting letters inside.
'mess' indicates an anagram.
'a'+'sad'='asad'
'asad' anagrammed gives 'saad'.
'l' inserted within 'saad' is 'SALAD'.
'with' acts as a link.
(Other definitions for salad that I've seen before include "A cold meal with lots of lettuce" , "A dish of lettuce and vegetables" , "Green, potato, Russian or Waldorf?" , "One that may be dressed for dinner" , "Cold vegetable dish" .)