Communist gives company bad dream (7)
I believe the answer is:
comrade
'communist' is the definition.
(I know that Comrade is a type of communist)
'company bad dream' is the wordplay.
'company' becomes 'co' (abbreviation).
'bad' indicates an anagram.
'dream' anagrammed gives 'mrade'.
'co'+'mrade'='COMRADE'
'gives' is the link.
(Other definitions for comrade that I've seen before include "Fellow soldier" , "Fellow socialist or good friend" , "Fellow left-winger" , "Ally" , "Colleague" .)