Basic bit of rig for joiner? (7)
I believe the answer is:
stapler
'for joiner?' is the definition.
(I've seen this in another clue)
'basic bit of rig' is the wordplay.
'basic' becomes 'staple' (synonyms).
'bit of' suggests taking the first letters.
The first letter of 'rig' is 'r'.
'staple'+'r'='STAPLER'
(Other definitions for stapler that I've seen before include "Implement for inserting paper fasteners" , "It's used to attach leaves" , "Paper fastener" , "Item of office equipment" , "Office equipment - plaster (anag)" .)