Lacking energy, attempted to reverse malicious gossip (4)
I believe the answer is:
dirt
'malicious gossip' is the definition.
(synonyms)
'lacking energy attempted to reverse' is the wordplay.
'lacking' is a deletion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'attempted' becomes 'tried' ('try' can be a synonym of 'attempt').
'to reverse' says the letters should be written in reverse.
'tried' with 'e' taken away is 'trid'.
'trid' written backwards gives 'DIRT'.
(Other definitions for dirt that I've seen before include "Obscenity" , "Grime - scandal" , "scandalous gossip" , "Scandalous info; earth" , "Grime - or controversial retention tax" .)