A lot of coral whistle-blower covers close to shore (4)
I believe the answer is:
reef
'a lot of coral' is the definition.
I can't tell whether this definition defines the answer.
'whistle-blower covers close to shore' is the wordplay.
'whistle blower' becomes 'ref' (I've seen this in other clues).
'covers' is an insertion indicator.
'close to' indicates one should take the final letters (the close of something is the end).
The last letter of 'shore' is 'e'.
'ref' placed around 'e' is 'REEF'.
Can you help me to learn more?
(Other definitions for reef that I've seen before include "Coral outcrop" , "Ridge of coral near the sea surface" , "The Great Barrier ..., Australian natural wonder" , "Shoal; take in (sail)" , "Ridge of rock just under water" .)