Old style readers enjoy these rather obvious openings (5)
I believe the answer is:
retro
'old style' is the definition.
'readers enjoy these rather obvious openings' is the wordplay.
'openings' suggests taking the first letters (I've seen 'opening of' mean this).
The first letters of 'readers enjoy these rather obvious' is 'RETRO'.
(Other definitions for retro that I've seen before include "Fashion reminiscent of the past" , "Backward looking" , "Associated with the past" , "Looking backwards" , "imitating past fashion" .)