The European mainland (unlike Britain) is chaste (9)
I believe the answer is:
continent
'is chaste' is the definition.
(similar in meaning)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for continent that I've seen before include "Europe, for one" , "Temperate - land mass" , "dry?" , "Large landmass" , "Monk vows" .)