Man, say, embracing diet finally providing fibre (5)
I believe the answer is:
istle
'fibre' is the definition.
(I've seen this before)
'man say embracing diet finally' is the wordplay.
'man say' becomes 'isle' (Isle of Man).
'embracing' is an insertion indicator.
'finally' indicates one should take the final letters.
The last letter of 'diet' is 't'.
'isle' enclosing 't' is 'ISTLE'.
'providing' is the link.
(Other definitions for istle that I've seen before include "Fibre from yucca or agave trees" , "Carpet material" , "for making nets?" .)