A love outwardly secure (4)
I believe the answer is:
nail
'secure' is the definition.
(both can mean to apprehend or capture)
'a love outwardly' is the wordplay.
'love' becomes 'nil' (love and nil mean zero in cricket and football).
'outwardly' is an insertion indicator.
'a' going inside 'nil' is 'NAIL'.
(Other definitions for nail that I've seen before include "Horny part of the digit" , "Spike, fasten" , "'For want of a . . . . the shoe was lost'" , "Metal pin, hit it on the head" , "What one has at one's fingertips" .)