Busts are developed but not easily perceived (8)
I believe the answer is:
abstruse
'not easily perceived' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs can occasionally define each other.
'busts are developed' is the wordplay.
'developed' indicates an anagram.
'busts'+'are'='bustsare'
'bustsare' anagrammed gives 'ABSTRUSE'.
'but' is the link.
Can you help me to learn more?
(Other definitions for abstruse that I've seen before include "Busts are oddly difficult to understand" , "Arcane" , "Strange busts are difficult to understand" , "Difficult to comprehend" , "Difficult to penetrate or understand" .)