Deathless seabird in wild lea (7)
I believe the answer is:
eternal
'deathless' is the definition.
(thesaurus)
'seabird in wild lea' is the wordplay.
'seabird' becomes 'tern' (tern is a kind of seabird).
'in' indicates putting letters inside.
'wild' indicates an anagram.
'lea' anagrammed gives 'eal'.
'tern' inserted into 'eal' is 'ETERNAL'.
(Other definitions for eternal that I've seen before include "non-stop" , "always to be remembered" , "Immortal" , "Not stopping" , "Ceaseless" .)