Summarise first cauliflower in harvest (5)
I believe the answer is:
recap
'summarise' is the definition.
(I know that recap is a more specific form of summarise)
'first cauliflower in harvest' is the wordplay.
'first cauliflower' becomes 'c' (1st letter of 'cauliflower').
'in' indicates putting letters inside.
'harvest' becomes 'reap' (synonyms).
'c' placed inside 'reap' is 'RECAP'.
(Other definitions for recap that I've seen before include "Go back over the main points" , "play again" , "cover the same ground again" , "Repeat of main points" , "Go over study material again" .)