Bark time, holding single weapon (7)
I believe the answer is:
bayonet
'weapon' is the definition.
(bayonet is a kind of weapon)
'bark time holding single' is the wordplay.
'bark' becomes 'bay' (baying is a kind of barking).
'time' becomes 't' (abbreviation).
'holding' means one lot of letters goes inside another.
'single' becomes 'one' (a single thing - only one).
'bay'+'t'='bayt'
'bayt' enclosing 'one' is 'BAYONET'.
(Other definitions for bayonet that I've seen before include "Knife fixed to the end of a rifle" , "Rifle attachment" , "Blade fixed to a rifle" , "Pointed weapon" , "Type of light bulb fitting" .)