Puts pressure on fasteners (6)
I believe the answer is:
places
'puts' is the definition.
('place' can be a synonym of 'put')
'pressure on fasteners' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'fasteners' becomes 'laces'.
'p'+'laces'='PLACES'
(Other definitions for places that I've seen before include "Locations" , "Sites" .)