Like a man's overheard secret (7)
I believe the answer is:
mystery
'secret' is the definition.
(I know that secret can be written as mystery)
'like a man's overheard' is the wordplay.
I cannot quite see how this works, but
'like' could be 'y' (similar in meaning) and 'y' is located in the answer.
'man's' could be 'ms' and 'ms' is located in the leftover letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for mystery that I've seen before include "Crime story" , "Something strange and inexplicable" , "Something hard to explain" , "A thing hard to explain" , "Mediaeval trade" .)