Bouncer using Circle Line after walk (10)
I believe the answer is:
trampoline
'bouncer' is the definition.
(I've seen this before)
'circle line after walk' is the wordplay.
'circle' becomes 'o'.
'after' means one lot of letters go next to another.
'walk' becomes 'tramp' (tramp is a kind of walk).
'o'+'line'='oline'
'oline' after 'tramp' is 'TRAMPOLINE'.
'using' is the link.
(Other definitions for trampoline that I've seen before include "Sprung gymnastic equipment" , "Trap oilmen (anag.)" , "bouncer" , "where pike may count in competition" , "Bouncy activity here" .)