Seductress learning to sleep in regularly (7)
I believe the answer is:
lorelei
'seductress' is the definition.
(thesaurus)
'learning to sleep in regularly' is the wordplay.
'learning' becomes 'lore' (I've seen this before).
'to' says to put letters next to each other.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'sleep'+'in'='sleepin'
The alternate letters of 'sleepin' are 'lei'.
'lore'+'lei'='LORELEI'
(Other definitions for lorelei that I've seen before include "Dangerous female" , "Fascinating women" , "Legendary siren and rock in the R Rhine" , "Siren of German legend who lured boatmen in the Rhine to destruction" , "Fatal nymph of the Rhine" .)