Jerk succeeded in climbing charts (5)
I believe the answer is:
spasm
'jerk' is the definition.
(I've seen this in another clue)
'succeeded in climbing charts' is the wordplay.
'succeeded' becomes 's' (genealogical abbreviation).
'in' is an insertion indicator.
'climbing' says the letters should be written backwards (in a down clue, letters climb up).
'charts' becomes 'maps' ('map' can be a synonym of 'chart').
'maps' reversed gives 'spam'.
's' placed into 'spam' is 'SPASM'.
(Other definitions for spasm that I've seen before include "Involuntary muscular movement" , "Burst" , "cramp" , "Involuntary contraction of muscles" , "Pretend to have (injury)" .)