A strain, working as craftsman (7)
I believe the answer is:
artisan
'craftsman' is the definition.
('artisan' can be a synonym of 'craftsman')
'a strain working' is the wordplay.
'working' is an anagram indicator.
'strain' with letters rearranged gives 'rtisan'.
'a'+'rtisan'='ARTISAN'
'as' is the link.
(Other definitions for artisan that I've seen before include "Skilled worker or craftsman" , "crafty person?" , "Skilled manual 17" , "Skilled tradesman" , "Technician" .)