Vacuous compassion I expressed after the writer tumbled over (5)
I believe the answer is:
empty
'vacuous' is the definition.
(I know that vacuous can be written as empty)
'after the writer tumbled over' is the wordplay.
'after' means one lot of letters go next to another.
'the writer' becomes 'me' (the person who wrote the clues).
'tumbled' is a reversal indicator.
'over' becomes 'pty' (I am not sure about this - if you are sure you should believe this answer much more).
'me' written backwards gives 'em'.
'em' put next to 'pty' is 'EMPTY'.
'compassion i expressed' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for empty that I've seen before include "(Of words) insincere" , "Loneliness parents feel when their children leave home" , "Containing nothing" , "Hollow or vacant" , "Dead man" .)