One with identical designation means Kea must be changed (8)
I believe the answer is:
namesake
'one with identical designation' is the definition.
'namesake' can be an answer for 'designation' (thesaurus). I am unsure of the 'one with identical' bit.
'means kea must be changed' is the wordplay.
'means' becomes 'names' (naming is a kind of meaning).
'must be changed' is an anagram indicator.
'kea' anagrammed gives 'ake'.
'names'+'ake'='NAMESAKE'
Can you help me to learn more?
(Other definitions for namesake that I've seen before include "One addressed in the same way" , "one similarly entitled" , "One's similarly entitled" , "What one may be called" , "One with the same appellation" .)