Like the hair of the dog, mostly? (5)
I believe the answer is:
curly
'like the hair' is the definition.
I can't tell whether this definition defines the answer.
'the dog mostly?' is the wordplay.
'the dog' becomes 'cur' (cur is a kind of dog).
'mostly?' becomes 'ly' (I can't explain this - if you can you should believe this answer much more).
'cur'+'ly'='CURLY'
'of' is the link.
Can you help me to learn more?
(Other definitions for curly that I've seen before include "Permed" , "Like a pig's tail" .)