A strict order that accepts one is aesthetically pleasing (8)
I believe the answer is:
artistic
'aesthetically pleasing' is the definition.
(I've seen this before)
'a strict order that accepts one' is the wordplay.
'order' indicates anagramming the letters.
'that accepts' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'strict' is an anagram of 'rtstic'.
'rtstic' enclosing 'i' is 'rtistic'.
'a'+'rtistic'='ARTISTIC'
'is' is the link.
(Other definitions for artistic that I've seen before include "Fine-looking" , "Aesthetic, creative" , "I stir cat (anag.)" , "Aesthetically pleasing" , "cultivated" .)