Trouble? A spot, not tons (3)
I believe the answer is:
ado
'trouble?' is the definition.
(thesaurus)
'a spot not tons' is the wordplay.
'spot' becomes 'dot' (I've seen this before).
'not' indicates named letters should be taken away.
'tons' becomes 't'.
'dot' with 't' removed is 'do'.
'a'+'do'='ADO'
(Other definitions for ado that I've seen before include "puff ball!" , "agitation" , "excitement" , "flapping" , "hoo-hah" .)