Singer in darkness during storm (11)
I believe the answer is:
Here is my best explanation:
'singer' is the definition.
(nightingale is a kind of birdanimal)
'darkness during storm' is the subsidiary indication.
'darkness' becomes 'night' (night is a kind of darkness).
'during' becomes 'in' (I've seen this in other clues).
'storm' becomes 'gale' (I've seen this before).
'in' is the link.
(Other definitions for nightingale that I've seen before include "Noted songbird", "Flier", "Bird noted for its song", "See 17", "Florence", "Celebrated songbird", "... bird", "Bird - famous nurse", "Bird with beautiful song" and "one tweets".)