Notice tyrant is missing from French (4)
I believe the answer is:
spot
'notice' is the definition.
(spot can mean to notice or observe)
'tyrant is missing from french' is the wordplay.
'tyrant' becomes 'despot' (synonyms).
'is missing' suggests deleting specific letters.
'from french' becomes 'de' ('from' in French).
'despot' with 'de' removed is 'SPOT'.
(Other definitions for spot that I've seen before include "moral flaw" , "place on TV programme" , "Discern - mark" , "Fix" , "Espy; mark" .)