She's expecting a family supplement (6-2-2)
I believe the answer is:
mother-to-be
'she's expecting' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for mother-to-be that I've seen before include "She's expecting" , "One expecting a baby" , "Expecting woman?" .)