встревать в разговор("Will you keep quiet!' 'Of course, of course.' 'You keep shoving your oar in – ''Sorry, sorry, shan't occur again." (P.G. Wodehouse) ART Vancouver)
на поверку("We extol the virtues of motherhood and bestow praise on the self-sacrificing homemaker but when push comes to shove, we give her little recognition for what she does" (Los Angeles Times). – Неопределённый артикль не употребляется. VLZ_58)