Remember Paddington? Popular personality (4,2,4)
I believe the answer is:
bear in mind
'remember' is the definition.
(to bear something in mind is to remember it)
'paddington? popular personality' is the wordplay.
'paddington?' becomes 'bear' (Paddington Bear is an example).
'popular' becomes 'in' (something that's 'in' is fashionable).
'personality' becomes 'mind' (mind can mean someone's personality).
'bear'+'in'+'mind'='BEAR IN MIND'
(Other definitions for bear in mind that I've seen before include "what big game hunter may have" , "Take into consideration" , "Remember and take into account" , "Consider" .)