Speak to adult about price (6)
I believe the answer is:
accost
'speak to' is the definition.
(thesaurus)
'adult about price' is the wordplay.
'adult' becomes 'a' (abbreviation).
'about' becomes 'c' (abbreviation for circa).
'price' becomes 'cost' (synonyms).
'a'+'c'+'cost'='ACCOST'
(Other definitions for accost that I've seen before include "Make bold approach to" , "Meet and greet" , "Approach, stop and speak to" , "Approach boldly or impudently" , "Come up and address" .)