Regretting destruction by force (5)
I believe the answer is:
ruing
'regretting' is the definition.
('rue' can be a synonym of 'regret')
'destruction by force' is the wordplay.
'destruction' becomes 'ruin' (ruin is a kind of destruction).
'by' says to put letters next to each other.
'force' becomes 'G' (short for gravity).
'ruin'+'g'='RUING'
(Other definitions for ruing that I've seen before include "full of remorse?" , "Feeling sorry for" , "feeling remorse" , "Regretful" , "Bitterly regretting" .)