What Meg and Doug do in close? (6)
I believe the answer is:
ending
'close?' is the definition.
(close is a kind of ending)
'what meg and doug do in' is the wordplay.
I cannot really see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is present in the answer.
'in' is present in the answer.
This explanation may well be incorrect...
(Other definitions for ending that I've seen before include "Bringing to a close" , "Finishing" , "Stopping" , "Finish" , "Putting a stop to" .)