To be safe, check out the dog (6)
I believe the answer is:
secure
'to be safe' is the definition.
('secure' can be a synonym of 'safe')
'check out the dog' is the wordplay.
'check' becomes 'see' ('see' can be a synonym of 'check').
'out' is an insertion indicator.
'the dog' becomes 'cur' (cur is a kind of dog).
'see' going around 'cur' is 'SECURE'.
(Other definitions for secure that I've seen before include "Fixed or fastened so as not to give way" , "Rescue (anag) - make safe" , "properly restrained" , "Firmly fixed or free from uncertainty" , "land" .)