Tactful, separate, we hear (8)
I believe the answer is:
discreet
'tactful' is the definition.
(similar in meaning)
'separate we hear' is the wordplay.
'separate' becomes 'discrete' (similar in meaning).
'we hear' shows a homophone (sound like).
'discrete' is a homophone of 'DISCREET'.
(Other definitions for discreet that I've seen before include "Careful in not attracting attention" , "Doesn't blab secrets, cautious" , "Cautious, not giving away secrets" , "Doesn't give away secrets - can be trusted" , "Tactful and trustworthy" .)