At the close of play, the match is ill-humoured (5)
I believe the answer is:
testy
'ill-humoured' is the definition.
Both the answer and definition are adjectives. Maybe there's an association between them I don't understand?
'at the close of play the match' is the wordplay.
'at' says to put letters next to each other.
'the close of play' becomes 'y' (closing letter of the word 'play').
'the match' becomes 'test' (as in a test match in cricket).
'y' put after 'test' is 'TESTY'.
'is' is the link.
Can you help me to learn more?
(Other definitions for testy that I've seen before include "Bad-tempered" , "Easily irritated" , "bad temper" , "Irascible" , "Captious" .)