Intense sorrow (4)
This clue is a double definition.
'intense' is the first definition.
(I've seen this in another clue)
'sorrow' is the second definition.
(thesaurus)
(Other definitions for keen that I've seen before include "Sharp -- express grief" , "Avid, enthusiastic" , "Quick" , "Piercing" , "Acute" .)
'intense sorrow' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for grief that I've seen before include "trouble" , "Distress" , "Suffering" , "Heartbreak" , "Deep sorrow" .)