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 the answer is hidden within the clue.
'LEE' can be found hidden inside '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" .)