Democrat with inadequate backing in decline (5)

I believe the answer is:

droop

I'm a little stuck... Click here to teach me more about this clue!

'decline' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for droop that I've seen before include "Go limp" , "sink" , "lose heart" , "Hang limply" , "Dangle" .)

I've seen this clue in The Sun and The Times.

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