Concealed hide close to sett (6)
I believe the answer is:
covert
'concealed' is the definition.
(similar in meaning)
'hide close to sett' is the wordplay.
'hide' becomes 'cover' (covering is a kind of hiding).
'close to' indicates one should take the final letters (the close/ending of).
The final letter of 'sett' is 't'.
'cover'+'t'='COVERT'
(Other definitions for covert that I've seen before include "Secret like fox's lair" , "Unacknowledged; thicket" , "Concealed, hidden" , "Thicket; not displayed" , "Not acknowledged" .)