Conceal a capital city on island (5)

I believe the answer is:

palma

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

'capital city on island' is the definition.
I can't judge whether this defines the answer.

'conceal a' is the wordplay.
'conceal' becomes 'palm' (I've seen this before).
'palm'+'a'='PALMA'

Can you help me to learn more?

(Other definitions for palma that I've seen before include "tourist centre in the Med" , "Town on Majorca" , "Port on Majorca" , "island capital" , "Capital of the Balearic Islands" .)

I've seen this clue in The Guardian.

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