Good relative has hired out a piece of armour (8)
I believe the answer is:
gauntlet
'out a piece of armour' is the definition.
I can't tell whether this defines the answer.
'good relative has hired' is the wordplay.
'good' becomes 'g' (abbreviation).
'relative' becomes 'aunt' (aunt is a kind of relative).
'has' is a charade indicator (letters next to each other).
'hired' becomes 'let' (I've seen this in other clues).
'g'+'aunt'+'let'='GAUNTLET'
Can you help me to learn more?
(Other definitions for gauntlet that I've seen before include "Throw it down to offer a challenge" , "Punishment to be run - heavy glove" , "Glove with long sleeve, thrown down challenge" , "Metal glove of medieval soldiers" , "Strong glove, thrown down in challenge" .)