Under raincoat the man's flash shows virility (8)
I believe the answer is:
machismo
'virility' is the definition.
(I've seen this before)
'under raincoat the man's flash' is the wordplay.
'under' says to put letters next to each other.
'raincoat' becomes 'mac' (mac is a kind of raincoat).
'the man's' becomes 'his' (I've seen this before).
'flash' becomes 'mo' (I've seen this in other clues).
'mac' put next to 'his' is 'machis'.
'machis'+'mo'='MACHISMO'
'shows' is the link.
(Other definitions for machismo that I've seen before include "show of masculinity" , "Cult of virility" , "The cult of masculine pride" , "Cult of masculinity" , "Agressive masculine pride" .)