This is held when fighting (6)
I believe the answer is:
shield
'fighting' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'this is held' is the wordplay.
'is held' anagrams to 'SHIELD'.
But, I am unsure how the anagram is indicated.
'when' is the link.
Can you help me to learn more?
(Other definitions for shield that I've seen before include "Protect or conceal" , "Protect (from danger)" , "Piece of armour carried on arm to protect body" , "Protect - prize" , "Protective covering" .)