To involve sheltering inside to prevent ailment (6)
I believe the answer is:
entail
'to involve' is the definition.
(entail means to involve or require)
'inside to prevent ailment' is the wordplay.
'inside' says the answer is hidden in the clue.
'ENTAIL' is hidden within 'to prevent ailment'.
'sheltering' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for entail that I've seen before include "Bring on, involve" , "Need" , "Bring on an inevitable consequence" , "Inalienable estate" , "Occasion" .)