Posture shown by beautifully elevated heads in a square formation (9)
I believe the answer is:
arabesque
'posture' is the definition.
(arabesque is a kind of posture)
'beautifully elevated heads in a square formation' is the wordplay.
'heads' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'formation' is an anagram indicator.
The first letters of 'beautifully elevated' is 'be'.
'a'+'square'='asquare'
'asquare' is an anagram of 'arasque'.
'be' put inside 'arasque' is 'ARABESQUE'.
'shown by' is the link.
(Other definitions for arabesque that I've seen before include "Short elaborate piece of music from Basque era" , "Ballet position - sea barque (anag)" , "Intertwined ornamental design" , "Move for dance" , "Ballet pose on one leg" .)