Item worn when eg, running dog gets fit (9)
I believe the answer is:
tracksuit
'item worn when eg running' is the definition.
I can't judge whether this defines the answer.
'dog gets fit' is the wordplay.
'dog' becomes 'track' (synonyms).
'gets' means one lot of letters go next to another.
'fit' becomes 'suit' (suiting is a kind of fitting).
'track'+'suit'='TRACKSUIT'
Can you help me to learn more?
(Other definitions for tracksuit that I've seen before include "athletic gear" , "Loose-fitting top and bottom for athlete warming up" , "Kit" , "Sportswear" , "Warm loose-fitting garment for exercising" .)