Cockney worker is a joiner (3)
I believe the answer is:
and
I believe this is a double definition.
'cockney worker' is the first definition.
('hand' - hand is a kind of worker - said with the 'H' dropped - a cockney accent.)
'a joiner' is the second definition.
(I've seen this before)
'is' acts as a link.
(Other definitions for and that I've seen before include "A very common conjunction" , "It's used to connect words, clauses or sentences" , "Together with" , "Word to connect" , "It connects words, clauses or sentences" .)