Moment where learner cuts identical card (9)
I believe the answer is:
twinkling
'moment' is the definition.
(I know that twinkling is a type of moment)
'learner cuts identical card' is the wordplay.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'cuts' means one lot of letters goes inside another (some letters cut their way into a word).
'identical' becomes 'twin' (I've seen this in another clue).
'card' becomes 'king' (type of playing card).
'twin'+'king'='twinking'
'l' inserted inside 'twinking' is 'TWINKLING'.
'where' acts as a link.
(Other definitions for twinkling that I've seen before include "Second" , "Instant" , "Bat of an eye" , "Shining intermittently" , "Jiffy" .)