Reckless general's assistant enthralled by chart (6)
I believe the answer is:
madcap
'reckless' is the definition.
(I've seen this in another clue)
'general's assistant enthralled by chart' is the wordplay.
'general's assistant' becomes 'adc' (aide de camp, assistant to a military officer).
'enthralled by' indicates putting letters inside ('enthral' can mean 'capture').
'chart' becomes 'map' (synonyms).
'adc' inserted within 'map' is 'MADCAP'.
(Other definitions for madcap that I've seen before include "Lunatic" , "Oddball" , "Amusingly crazy (person)" , "Eccentric or reckless person" , "Hare-brained" .)