Being handy, guest regularly rebuilt flue (6)
I believe the answer is:
useful
'being handy' is the definition.
(I've seen this before)
'guest regularly rebuilt flue' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'rebuilt' indicates anagramming the letters.
The alternate letters of 'guest' are 'us'.
'flue' with letters rearranged gives 'eful'.
'us'+'eful'='USEFUL'
(Other definitions for useful that I've seen before include "Handy; very able" , "Make yourself . . . . . . - help out" , "Functional, handy" , "Proficient; handy" , "Functional and worthwhile" .)