Arrive after a shower perhaps and confess (4,5)
I believe the answer is:
come clean
'confess' is the definition.
(I've seen this before)
'arrive after a shower perhaps and' is the wordplay.
'arrive' becomes 'come' (synonyms).
'after' is a charade indicator (letters next to each other).
'a shower perhaps' becomes 'clea' (I can't justify this - if you can you should believe this answer much more).
'and' becomes 'n' (common abbreviation for 'and').
'come'+'clea'+'n'='COME CLEAN'
Can you help me to learn more?
(Other definitions for come clean that I've seen before include "Confess fully or arrive after ablutions" , "how you hope your home delivery laundry will arrive" , "Make honest admission" , "Informally, confess fully - arrive washed?" , "Fully confess something" .)