It's played up or down (5)
I believe the answer is:
darts
'down' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'it's played up' is the wordplay.
I cannot really see how this works, but
'it's' could be 'ts' (abbreviation. e.g. in 'tis) and 'ts' is found in the answer.
The remaining letters 'dar' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'or' acts as a link.
Can you help me to learn more?
(Other definitions for darts that I've seen before include "Traditional pub game" , "They are thrown at targets in pubs" , "Tears" , "Game in which missiles are thrown at target" , "Game with board and missiles" .)