Pursues one of two options? (5)
I believe the answer is:
tails
This clue is a double definition.
'pursues' is the first definition.
(tailing is a kind of pursuing)
'one of two options?' is the second definition.
(heads or tails)
(Other definitions for tails that I've seen before include "the back of bears - bulls too" , "Ends" , "Animals' extremities" , "Follows closely" , "A possible fall of the pound" .)