Sequence of Trump’s initial downfall (5)
I believe the answer is:
train
'sequence' is the definition.
(I've seen this before)
'trump's initial downfall' is the wordplay.
'initial' indicates taking the first letters.
'downfall' becomes 'rain' (rain is a kind of downfall).
The first letter of 'trumps' is 't'.
't'+'rain'='TRAIN'
'of' acts as a link.
(Other definitions for train that I've seen before include "Public transport on the railway" , "Teach; series of gears" , "one thing after another" , "Trailing material on dress" , "Railway engine" .)