To give protection from French fiend, I must go (6)
I believe the answer is:
defend
'to give protection' is the definition.
'from french fiend i must go' is the wordplay.
'from french' becomes 'de' (French for 'from').
'must go' indicates named letters should be taken away.
'fiend' with 'i' removed is 'fend'.
'de'+'fend'='DEFEND'
(Other definitions for defend that I've seen before include "Represent the accused" , "Justify" , "Help or protect against attack" , "Protect, fight back" , "Maintain against attack" .)