In public, shirt ambassador's put on is immoderate (4-3-3)
I believe the answer is:
over-the-top
'on is immoderate' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'in public shirt ambassador's' is the wordplay.
'in' means one lot of letters goes inside another.
'public' becomes 'overt' (both can mean well-known or unconcealed).
'shirt' becomes 'top' (I've seen this in another clue).
'ambassador' becomes 'HE' (His or Her Excellency).
'overt'+'top'='overttop'
'overttop' placed around 'he' is 'OVER-THE-TOP'.
'put' acts as a link.
Can you help me to learn more?
(Other definitions for over-the-top that I've seen before include "Theatrically excessive" , "Excessively extreme" , "To an exaggerated degree" .)