Bed gets a layer of paint (4)
I believe the answer is:
coat
'layer of paint' is the definition.
(I've seen this before)
'bed gets a' is the wordplay.
'bed' becomes 'cot' (cot is a kind of bed).
'gets' is an insertion indicator (gets can mean captures or absorbs).
'cot' placed around 'a' is 'COAT'.
(Other definitions for coat that I've seen before include "Jacket" , "Apply layer" , "Warm outerwear" , "Layer of paint" , "blanket" .)