Male ballet star regrets day taken up penning article (7)
I believe the answer is:
danseur
'male ballet star' is the definition.
The definition suggests a singular noun which matches the answer.
'regrets day taken up penning article' is the wordplay.
'regrets' becomes 'rues' ('rue' can be a synonym of 'regret').
'day' becomes 'd' (abbreviation for day).
'taken up' says the letters should be written backwards.
'penning' is an insertion indicator.
'article' becomes 'an' (indefinite article).
'rues'+'d'='ruesd'
'ruesd' written backwards gives 'dseur'.
'dseur' placed around 'an' is 'DANSEUR'.
Can you help me to learn more?
(Other definitions for danseur that I've seen before include "Male ballet dancer, partner of a ballerina" , "Ballet star" , "Participant in The Rite of Spring perhaps" , "Man in ballet" , "Male ballet performer" .)