Bath, say, having reduced width (3)
I believe the answer is:
spa
'bath say' is the definition.
(a spa is a type of bath)
'reduced width' is the wordplay.
'reduced' means to remove the last letter.
'width' becomes 'span' (span between two points).
'span' with its last letter taken off is 'SPA'.
'having' is the link.
(Other definitions for spa that I've seen before include "here for healthy holiday" , "A therapeutic hot spring" , "eg Bath" , "place of treatment" , "Heated bath" .)