Flower expert miles off (5)

I believe the answer is:

aster

I'm a little stuck... Click here to teach me more about this clue!

'flower' is the definition.
(aster is a kind of flower)

I don't understand how the rest of the clue works.

(Other definitions for aster that I've seen before include "bloomer" , "Daisy-like garden flower" , "Garden plant" , "Purple pink flowered plant" , "Plant of Michaelmas daisy family" .)

I've seen this clue in The Telegraph.

Want a hint initially instead of a full solution? Install my app