Messing about, did mistakenly throw out (8)
I believe the answer is:
fiddling
'messing' is the definition.
Although both the answer and definition are present participle verbs, I can't see how one could define the other.
'did mistakenly throw out' is the wordplay.
'mistakenly' indicates an anagram.
'throw' becomes 'fling' (flinging is a kind of throwing).
'out' indicates putting letters inside.
'did' anagrammed gives 'idd'.
'idd' inserted within 'fling' is 'FIDDLING'.
'about' acts as a link.
Can you help me to learn more?
(Other definitions for fiddling that I've seen before include "trivial" , "Such swindles may be" , "What Nero was doing while Rome burned" , "Tinkering - trifling" , "petty" .)