Nuns' rig designed for looking after the sick (7)
I believe the answer is:
nursing
'looking after the sick' is the definition.
I can't judge whether this definition defines the answer.
'nuns' rig designed' is the wordplay.
'designed' is an anagram indicator (designed with the letters).
'nuns'+'rig'='nunsrig'
'nunsrig' with letters rearranged gives 'NURSING'.
'for' is the link.
Can you help me to learn more?
(Other definitions for nursing that I've seen before include "Caring profession" , "now a graduate profession" , "Medical vocation" , "Caring career" , "Feeding baby" .)