On certain days, these teams are slow starters! (5)
I believe the answer is:
sides
'starters' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Maybe you can see an association between them that I can't see?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for sides that I've seen before include "Teams or flat surfaces" , "Sports teams" , "Opposing teams or facets" , "Lines" , "More than one team" .)