One nursing a relative? (6)

I believe the answer is:

sister

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

'a relative?' is the definition.
(I know that sister is a type of first-degree relative)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for sister that I've seen before include "Relative in hospital?" , "Resist about the sibling" , "Nurse, nun and sibling" , "Member of family" , "Martin --, film director" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app