Careless fellow following German during line dancing (9)
I believe the answer is:
negligent
'careless' is the definition.
('negligent' can be similar in meaning to 'careless')
'fellow following german during line dancing' is the wordplay.
'fellow' becomes 'gent' (I've seen this before**).
'following' says to put letters next to each other.
'german' becomes 'g' (abbreviation).
'during' is an insertion indicator.
'dancing' indicates an anagram.
'line' with letters rearranged gives 'neli'.
'g' put within 'neli' is 'negli'.
'gent' put after 'negli' is 'NEGLIGENT'.
(Other definitions for negligent that I've seen before include "Careless, remiss" , "Not minding" , "Failing to take proper care" , "Failing to take due care" , "slack" .)