Footballer backing county they never forget (9)
I believe the answer is:
elephants
'they never forget' is the definition.
The definition suggests an adverb but the answer is not.
'footballer backing county' is the wordplay.
'footballer' becomes 'pele' (Brazilian footballer Pele).
'backing' shows that the letters should be reversed in order.
'county' becomes 'hants' (short for Hampshire).
'pele' reversed gives 'elep'.
'elep'+'hants'='ELEPHANTS'
Can you help me to learn more?
(Other definitions for elephants that I've seen before include "Five-toed pachyderms" , "Largest animals" , "See 16" , "Jumbos" , "The planes (anag.)" .)