Son has unfinished model to spray (7)
I believe the answer is:
spatter
'spray' is the definition.
(I've seen this before)
'son has unfinished model' is the wordplay.
'son has' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'unfinished' means to remove the last letter.
'model' becomes 'pattern' (pattern is a kind of model).
'pattern' with its last letter taken off is 'patter'.
's'+'patter'='SPATTER'
'to' is the link.
Can you help me to learn more?
(Other definitions for spatter that I've seen before include "Set part (anag.)" , "Cover with droplets" , "spray" , "Sprinkle" , "shower" .)