Hostile and cool on returning after tip from Mad Hatter (8)
I believe the answer is:
milliner
'mad hatter' is the definition.
'milliner' can be an answer for 'hatter' (synonyms). I'm not sure about the 'mad' bit.
'hostile and cool on returning after tip' is the wordplay.
'hostile' becomes 'ill' (ill can mean harmful or damaging).
'and' says to put letters next to each other.
'cool' becomes 'in' ('in' can mean fashionable or cool).
'on' is an insertion indicator.
'returning after tip' becomes 'mer' (I can't explain this - if you can you should believe this answer much more).
'ill'+'in'='illin'
'illin' going inside 'mer' is 'MILLINER'.
'from' is the link.
Can you help me to learn more?
(Other definitions for milliner that I've seen before include "One making pork-pies" , "Felt cutter perhaps" , "Hat-maker" , "Ladies' hatter" , "Garment maker" .)