Coolness of pal stoned by ugly mob (6)
I believe the answer is:
aplomb
'coolness' is the definition.
(I've seen this before)
'pal stoned by ugly mob' is the wordplay.
'stoned' indicates an anagram (can mean on drugs or drunk).
'by' says to put letters next to each other.
'ugly' is an anagram indicator.
'pal' is an anagram of 'apl'.
'mob' with letters rearranged gives 'omb'.
'apl'+'omb'='APLOMB'
'of' is the link.
(Other definitions for aplomb that I've seen before include "'Poise, sang-froid (6)'" , "Self-satisfied dignity and confidence" , "Self-satisfied dignity, complacency" , "Calm self-assurance and poise" , "Self confidence" .)