Reveal all after country club investigation quietly dropped (6)
I believe the answer is:
unrobe
'reveal all' is the definition.
(remove clothing)
'country club investigation quietly dropped' is the wordplay.
'country club' becomes 'UN' (United Nations, group of countries).
'investigation' becomes 'probe' (probe can mean an investigation or inquiry).
'quietly' becomes 'p' (p for piano and quiet).
'dropped' suggests deleting specific letters (some letters are excluded or dropped).
'probe' with 'p' taken away is 'robe'.
'un'+'robe'='UNROBE'
'after' acts as a link.
(Other definitions for unrobe that I've seen before include "Remove an item of clothing" , "strip" .)