Comfortable when weapons are returned (4)
I believe the answer is:
snug
'comfortable' is the definition.
(similar in meaning)
'weapons are returned' is the wordplay.
'weapons' becomes 'guns' (gun is a kind of weapon).
'are returned' says the letters should be written in reverse.
'guns' in reverse letter order is 'SNUG'.
'when' acts as a link.
(Other definitions for snug that I've seen before include "Cosy room" , "Close-fitting and cosy" , "Bar-parlour" , "He joined" , "Comfortable with guns" .)