Repeated word in a Doris Day hit (4)
I believe the answer is:
sera
'repeated word in a doris day hit' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sera that I've seen before include "Watery liquids" , "Bodily fluids (following 'que'?)" , "Hospital supplies" , "Sear with serums" .)