Club beaten learns to defend area (7)
I believe the answer is:
arsenal
'club' is the definition.
(I've seen this before)
'beaten learns to defend area' is the wordplay.
'beaten' is an anagram indicator (letters beaten up or destroyed).
'to defend' means one lot of letters goes inside another.
'area' becomes 'a' (maths abbreviation).
'learns' with letters rearranged gives 'arsenl'.
'arsenl' enclosing 'a' is 'ARSENAL'.
(Other definitions for arsenal that I've seen before include "Weapons/ammo store" , "Eleven" , "team effort" , "Munitions store and English football team" , "Football club and military store" .)