Couple carry on showing double thickness (3-3)
I believe the answer is:
two-ply
'double thickness' is the definition.
'two ply' can be an answer for 'double' (thesaurus). I'm not certain of the 'thickness' bit.
'couple carry on' is the wordplay.
'couple' becomes 'two' (two people or things).
'carry on' becomes 'ply' (ply can mean to work continually at something).
'two'+'ply'='TWO-PLY'
'showing' acts as a link.
Can you help me to learn more?
(Other definitions for two-ply that I've seen before include "Like soft loo paper?" , "Wood made by gluing one layer on another" , "Woven double" .)