Kit with myxomatosis ultimately left blind (10)
I believe the answer is:
sportswear
'kit' is the definition.
(I've seen this before)
'myxomatosis ultimately left blind' is the wordplay.
'ultimately' suggests the final letters.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'blind' becomes 'swear' ('blind' means 'swear' as in 'effing and blinding').
The final letter of 'myxomatosis' is 's'.
's'+'port'+'swear'='SPORTSWEAR'
'with' acts as a link.
(Other definitions for sportswear that I've seen before include "Clothing" , "Gear" , "informal suits" , "clothes for play" , "in which triathletes swim" .)