Protection from undesirable exposure (3)
I believe the answer is:
lee
'protection' is the definition.
(I've seen this before)
'from undesirable exposure' is the wordplay.
'from' indicates a hidden word.
'LEE' is hidden within 'undesirable exposure'.
(Other definitions for lee that I've seen before include "The sheltered side of something" , "Confederate general" , "Area sheltered from the wind" , "Sheltered from the wind in Cork, perhaps" , "Shelter" .)