It may display extremes of virility, essential with trim (7)
I believe the answer is:
vandyke
'it may display extremes of virility essential' is the definition.
The definition suggests a singular noun which matches the answer.
'with trim' is the wordplay.
I cannot quite see how this works, but
'with' could be 'and' and 'and' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for vandyke that I've seen before include "Broad eighteenth-century lace collar" , "Broad linen collar" , "Lace collar; beard" , "Flemish painter with short pointed beard" , "Pointed lace collar (after Flemish painter)" .)