Crossword Genius

Flip over how big an accessory is? (7)

Ross

I believe the answer is:

capsize

'flip over' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

(Other definitions for capsize that I've seen before include "Of boat, turn turtle" , "Overturn (a boat)" , "Upset" , "Turn so that keel faces upwards" .)

I've seen this clue in The Guardian.
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