Egg layer had nice waves (7)
I believe the answer is:
echidna
'egg layer' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'had nice waves' is the wordplay.
'waves' is an anagram indicator.
'had'+'nice'='hadnice'
'hadnice' anagrammed gives 'ECHIDNA'.
Can you help me to learn more?
(Other definitions for echidna that I've seen before include "Spiny Aus. mammal" , "Little animal" , "Prickly creature" , "Oz native" , "Spiny egg-laying Australian mammal" .)