Appropriate opening of zoo with Mr Durrell, a writer (10)
I believe the answer is:
fitzgerald
'a writer' is the definition.
(F Scott Fitzgerald)
'appropriate opening of zoo with mr durrell' is the wordplay.
'appropriate' becomes 'fit' ('fit' can be similar in meaning to 'appropriate').
'opening of' suggests taking the first letters.
'with' is a charade indicator (letters next to each other).
'mr durrell' becomes 'gerald' (Gerald Durrell).
The initial letter of 'zoo' is 'z'.
'fit'+'z'+'gerald'='FITZGERALD'
(Other definitions for fitzgerald that I've seen before include "poet" , "Ella --, singer" , "F. Scott -, US author (The Great Gatsby)" , "Novelist who wrote The Great Gatsby" .)