Subject those people memorise at last (5)
I believe the answer is:
theme
'subject' is the definition.
(synonyms)
'those people memorise at last' is the wordplay.
'those people' becomes 'them' (I've seen this before).
'at last' suggests the final letters.
The final letter of 'memorise' is 'e'.
'them'+'e'='THEME'
(Other definitions for theme that I've seen before include "[(type of) PARK]" , "(Writer's) topic" , "Motif - 4 across" , "Subject of a talk or piece of writing" , "Subject (of talk, text, etc)" .)