Exceptional or especially normal (13)
I believe the answer is:
extraordinary
'exceptional' is the definition.
(similar in meaning)
'especially normal' is the wordplay.
'especially' becomes 'extra' (synonyms).
'normal' becomes 'ordinary' (I've seen this before).
'extra'+'ordinary'='EXTRAORDINARY'
'or' is the link.
(Other definitions for extraordinary that I've seen before include "Remarkable - abnormal" , "Highly unusual" , "Phenomenal" , "Exceptional" .)