Don't forget imaginary teddy (4,2,4)
I believe the answer is:
bear in mind
'don't' is the definition.
Both the definition and answer are verbs in their base form.
Perhaps they are linked in a way I don't understand?
'forget imaginary teddy' is the wordplay.
I cannot quite see how this works, but
'imaginary' could be 'inmind' and 'inmind' is found within the answer.
'teddy' could be 'bear' and 'bear' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bear in mind that I've seen before include "Remember and take into account" , "Consider" , "Take into consideration" , "what big game hunter may have" .)