Brass tacks (4,3,5)
I believe the answer is:
nuts and bolts
'brass tacks' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for nuts and bolts that I've seen before include "available from hardware store" , "Fundamentals" , "Essential basics" , "DDessentials of the ironmonger's trade?" , "Basics - fasteners?" .)