Companion’s left cold and sick (3)
I believe the answer is:
ill
'sick' is the definition.
(I know that sick can be written as ill)
'companion's left cold' is the wordplay.
'companion' becomes 'ch' (Companion of Honour).
'left' suggests deleting specific letters.
'cold' becomes 'chill' (chill can mean cold).
'chill' with 'ch' taken away is 'ILL'.
'and' is the link.
(Other definitions for ill that I've seen before include "Harmful" , "Unhealthy" , "Wicked" , "laid up?" , "Faulty" .)