The most common and most likely answer to this crossword clue is the 7 letter word GRAMPUS
I've seen this crossword clue in Independent
G
R
A
M
P
U
S
More clues leading to the result GRAMPUS
- Heavy breather coming round to eat spread
- Skilful swimmer's weight - with special effort - reduced
- Whale to blow endlessly, about to rise?
- Medic bandages male American sea creature
- Drink spread around by marine mammal
- Lightweight Manx cat’s a killer at sea
- Aquatic animal showing mass discharge
- Politician covered in melted sugar – this is at home in the main
Buddy explains!

The straight part
We know that "Whale" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case whale = grampus.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does GRAMPUS mean?
GRAMPUS noun- The killer whale, Orcinus orca.
- Risso's dolphin, Grampus griseus, with a blunt nose.
- The hellbender salamander, Cryptobranchus alleganiensis.
- Giant whip scorpion (Mastigoproctus giganteus)