Opening a fresh source of water in Yorkshire (8)
I believe the answer is:
aperture
'opening' is the definition.
(I know that aperture is a type of aperture)
'a fresh source of water in yorkshire' is the wordplay.
'fresh' becomes 'pert' (I've seen this before).
'source of water in yorkshire' becomes 'ure' (I am not sure about this - if you are sure you should believe this answer much more).
'a'+'pert'+'ure'='APERTURE'
Can you help me to learn more?
(Other definitions for aperture that I've seen before include "Opening, mostly small" , "Narrow opening" , "'Hole, opening (8)'" , "Eye" , "Opening (for a photographer?)" .)