Male ego of Scot confronting his doctor (8)
I believe the answer is:
Here is my best explanation:
'male ego' is the definition.
'scot confronting his doctor' is the subsidiary indication.
'scot' becomes 'mac' (many Scottish surnames begin with Mac).
'confronting' is a charade indicator (letters next to each other).
'doctor' becomes 'mo' (medical officer**).
'of' is the link.
(Other definitions for machismo that I've seen before include "virile obsession", "Masculine swagger", "large injection of testosterone!", "Agressive masculine pride", "Exaggerated masculinity", "Masculinity", "Exaggerated virility", "Virility", "show of masculinity" and "Exaggerated masculine pride".)