Checks foundation garments (5)
I believe the answer is:
stays
I believe this clue is a triple definition!
'checks' is the first definition.
(I know this)
'foundation' is the second definition.
(stays is a kind of foundation)
'garments' is the third definition.
(I have seen 'restrictive garments' mean 'stays' so perhaps 'garments' could also mean 'stays')
(Other definitions for stays that I've seen before include "restrictive garments" , "Remains (in place)" , "old underwear" , "Old-fashioned corset" , "Guys; remains" .)