Highest-ranking officers taking to soft metal (3,5)
I believe the answer is:
top brass
'highest-ranking officers' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'to soft metal' is the wordplay.
'soft' becomes 'p' (musical abbreviation for 'piano').
'metal' becomes 'brass' (brass is a kind of metal).
'to'+'p'+'brass'='TOP-BRASS'
'taking' acts as a link.
Can you help me to learn more?
(Other definitions for top brass that I've seen before include "VIPs" , "most important officials" , "Most important leaders, officers, etc" , "military leaders" , "High-ranking figures of authority" .)