Pro athlete suppresses vulgar outburst (4)
I believe the answer is:
oath
'vulgar outburst' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?
'pro athlete suppresses' is the wordplay.
'suppresses' indicates the answer is hidden within the clue (the clue suppresses or covers up the answer).
'OATH' is hidden within 'pro athlete'.
Can you help me to learn more?
(Other definitions for oath that I've seen before include "Vow or expletive" , "Strong language" , "exasperated comment" , "darn, for example" , "Swear word" .)