Asks in Spanish what interrupts siestas (8)
I believe the answer is:
requests
'asks' is the definition.
('request' can be a synonym of 'ask')
'spanish what interrupts siestas' is the wordplay.
'spanish what' becomes 'que' ('what' in Spanish).
'interrupts' is an insertion indicator.
'siestas' becomes 'rests' (I am not sure about this - if you are sure you should believe this answer much more).
'que' inserted within 'rests' is 'REQUESTS'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for requests that I've seen before include "demands" , "Asks for" , "Applies" , "Supplications" , "Petitions" .)