The fellow has a right to be furtive (6)
I believe the answer is:
covert
'be furtive' is the definition.
(I've seen this before)
'the fellow has a right' is the wordplay.
'the fellow' becomes 'cove' (British slang term**).
'has' means one lot of letters go next to another.
'a right' becomes 'rt'.
'cove'+'rt'='COVERT'
'to' is the link.
(Other definitions for covert that I've seen before include "Thicket; not displayed" , "Hidden - thicket" , "Not openly displayed" , "Concealed, like fox's lair" , "Undercover; thicket" .)