Clothing that's out of service (7)
I believe the answer is:
civvies
'clothing' is the definition.
(civvies is a kind of clothing)
'that's out of service' is the wordplay.
I cannot quite see how this works, but
'that's' could be 'ie' and 'ie' is found in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for civvies that I've seen before include "Mufti" , "those not in service" , "Non-uniform" , "Non-military attire" , "Non-military clothes for ex-army personnel" .)