Joiner employed in B&Q (9)
I believe the answer is:
ampersand
'joiner' is the definition.
(the 'and' symbol - something which joins things)
I don't understand the rest of the clue.
(Other definitions for ampersand that I've seen before include "Character representing "and"" , "that is seen at the keyboard" , "Plus sign" , "character (sharing with 7)" , "It connects" .)