The lady left the empty, open relic for protection (7)
I believe the answer is:
shelter
'for protection' is the definition.
(shelter is a kind of protection)
'the lady left the empty open relic' is the wordplay.
'the lady left' becomes 'shel' (I can't explain this - if you can you should give a lot more credence to this answer).
'empty' suggests removing the centre.
'open' says to take the initial letters (take the opening letter).
'the' with its centre taken out is 'te'.
The initial letter of 'relic' is 'r'.
'shel'+'te'+'r'='SHELTER'
Can you help me to learn more?
(Other definitions for shelter that I've seen before include "Protective structure" , "Shield as from rain" , "Monk's hood" , "Refuge or protective cover" , "Roof" .)