Wild lions have big head, that’s capital (6)
I believe the answer is:
lisbon
'capital' is the definition.
(Lisbon is an example)
'wild lions have big head' is the wordplay.
'wild' indicates anagramming the letters.
'have' indicates putting letters inside.
'head' says to take the initial letters.
The first letter of 'big' is 'b'.
'lions' with letters rearranged gives 'lison'.
'lison' enclosing 'b' is 'LISBON'.
'that's' acts as a link.
(Other definitions for lisbon that I've seen before include "Capital of Portugal" , "Capital city on the Tagus" , "Portuguese capital" , "Slob in Portuguese city" , "Capital city and Treaty" .)