Batten down firm (6)
I believe the answer is:
secure
I believe this clue is a double definition.
'batten down' is the first definition.
(I know that batten down can be written as secure)
'firm' is the second definition.
(similar in meaning)
(Other definitions for secure that I've seen before include "Stable" , "Rescue (anag) - make safe" , "Free from danger or risk" , "properly restrained" , "Obtain - safe" .)