Hurried departure of heartless idiot going by land (9)
I believe the answer is:
moonlight
'hurried departure' is the definition.
(moonlight can mean a late-night departure)
'heartless idiot going by land' is the wordplay.
'heartless' means to remove the middle letters.
'idiot' becomes 'moron' (synonyms).
'going by land' becomes 'light' (I am not sure about this - if you are sure you should believe this answer much more).
'moron' with its centre removed is 'moon'.
'moon'+'light'='MOONLIGHT'
'of' is the link.
Can you help me to learn more?
(Other definitions for moonlight that I've seen before include "piano piece" , "Work late" , "Illumination from the earth's satellite" , "Secretly work" , "Lunar rays seen in thin gloom" .)