Relief organisation is nervous about it (7)
I believe the answer is:
charity
'relief organisation' is the definition.
(a charity provides relief)
'nervous about it' is the wordplay.
'nervous' becomes 'chary' (chary means nervous or cautious).
'about' indicates putting letters inside.
'chary' placed around 'it' is 'CHARITY'.
'is' acts as a link.
(Other definitions for charity that I've seen before include "Love" , "Help for needy" , "Gifts to the needy" , "Behaviour of the kind" , "A good cause" .)