Dog that’s a boon, following bachelor (6)
I believe the answer is:
basset
'dog' is the definition.
(basset is a kind of dog)
'a boon following bachelor' is the wordplay.
'a boon' becomes 'asset' (I've seen this before).
'following' says to put letters next to each other.
'bachelor' becomes 'b' (abbreviation e.g. BA=Bachelor of Arts).
'asset' after 'b' is 'BASSET'.
'that's' is the link.
(Other definitions for basset that I've seen before include "Sturdy hunting dog" , "Hound with short legs and long ears" , "Hare-hunting hound among beasts" , "Low, smooth-haired breed of hound" , "Smooth-haired, long-eared hound" .)