How to get down from a whale? (4)
I believe the answer is:
blue
'a whale?' is the definition.
(blue whale is a kind of whale)
I don't understand the remainder of the clue.
(Other definitions for blue that I've seen before include "adult" , "Turquoise, say" , "very cold" , "It's used to whiten laundry" , "sometimes heard of with little boy" .)