Find out what goose eggs contain (3)
I believe the answer is:
see
'find out' is the definition.
(I know that find out can be written as see)
'what goose eggs contain' is the wordplay.
'contain' indicates a hidden word (words from the clue contain the answer).
'SEE' is hidden within 'what goose eggs'.
(Other definitions for see that I've seen before include "Witness; ensure" , "Look at the bishop's domain" , "Observe the bishop's domain" , "Observe - diocese" , "Observe the papacy in Rome" .)