In ecstasy about art pen (6)
I believe the answer is:
enrapt
'in ecstasy' is the definition.
(I've seen this before)
'about art pen' is the wordplay.
'about' indicates anagramming the letters.
'art'+'pen'='artpen'
'artpen' is an anagram of 'ENRAPT'.
(Other definitions for enrapt that I've seen before include "Spellbound" , "Fascinated" , "Sent" , "Turned on" , "Deeply absorbed in something" .)