Evidence of sickness in canary, weary (6,4)
I believe the answer is:
yellow flag
'evidence of sickness' is the definition.
(maritime flag used to show sickness)
'canary weary' is the wordplay.
'canary' becomes 'yellow' (type of yellow).
'weary' becomes 'flag' (both can mean to tire).
'yellow'+'flag'='YELLOW FLAG'
'in' acts as a link.
(Other definitions for yellow flag that I've seen before include "Signal letter Q, flown to indicate ship is carrying disease" , "Signal of quarantined ship - wild iris" .)