Sons go before church sermon (6)
I believe the answer is:
speech
'sermon' is the definition.
(thesaurus)
'sons go before church' is the wordplay.
'sons' becomes 's'.
'go' becomes 'pee' (both can mean to urinate).
'before' says to put letters next to each other.
'church' becomes 'ch' (common abbreviation).
's'+'pee'+'ch'='SPEECH'
(Other definitions for speech that I've seen before include "words" , "Vocal communication" , "'Utterance, talk (6)'" , "Formal discourse to an audience" , "Talk given to an audience" .)