What a wandering poet thought lacking company is obscure (5)
I believe the answer is:
cloud
This clue is a double definition.
'what a wandering poet thought lacking company' is the first definition.
('I wandered lonely as a cloud', William Wordsworth)
'obscure' is the second definition.
(clouding is a kind of obscuring)
'is' is the link.
(Other definitions for cloud that I've seen before include "Condensed air vapour" , "''I wandered lonely as a ...'' (Wordsworth)" , "Visible vapour in sky" , "E.g. stratus" , "Source of rain" .)