Bungling writer going north in it (5)
I believe the answer is:
inept
'bungling' is the definition.
(synonyms)
'writer going north in it' is the wordplay.
'writer' becomes 'pen' (something which writes).
'going north' says the letters should be written in reverse.
'in' indicates putting letters inside.
'pen' in reverse letter order is 'nep'.
'nep' put within 'it' is 'INEPT'.
(Other definitions for inept that I've seen before include "Standard required in a piece of work (colloq.)" , "Not competent" , "Unskilful or unsuitable" , "Incompetent and ineffectual" , "Unskilful, awkward" .)