The most common and most likely answer to this crossword clue is the 5 letter word VENUS
I've seen this crossword clue in Independent
V
E
N
U
S
More clues leading to the result VENUS
- Goddess of certain vessels, you could say
- See eastern star rising — or planet
- Five English students getting the Morning Star
- Places overlooking Earth and its neighbour
- Locations losing last English mollusc
- Deity in heaven, usually
- Goddess who’s in heaven, usually
- Archdeacon attending American Beauty
- Sex goddess very exciting at first to students
- Concert halls in which Electronic cancelled second appearance
Buddy explains!

The straight part
We know that "mollusc (Venus-shell)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mollusc (venus-shell) = venus.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.