French are binding feet for amphibians (4)
I believe the answer is:
efts
'amphibians' is the definition.
(eft is a kind of amphibian)
'french are binding feet' is the wordplay.
'french are' becomes 'es' ('are' in French).
'binding' means one lot of letters goes inside another.
'feet' becomes 'ft' (abbreviation).
'es' enclosing 'ft' is 'EFTS'.
'for' acts as a link.
(Other definitions for efts that I've seen before include "Amphibians" , "Baby newts" , "Kind of newts" , "Old lizards" .)