Can a clue giver let team know they are almost right?
I struggled to find a copy of the printed rules for this online, only various guide.  There is a Rules summary on BGG that clear says -

The Clue Giver cannot use hand gestures

So 'rolling his hands' is technically against the rules.
I also wouldn't say &quot;that word is right&quot;. because in the example you gave it wasn't.   I can't see anything in the rules that says you can't say &quot;that's almost right&quot;
The important thing to remember is you playing a fun party game.   In games like this if a player becomes to strict and rules lawyering that it stops being fun.  If a player makes a minor rules violation then keep it fun and let it go the first time.  In the UK there is a radio show called &quot;Just a Minute&quot; which is a silly party game.  when players do minor things wrong the Host gives player &quot;The benefit of the doubt&quot; to let players get away with small things but that they will try to redress later.  I think this is good practice in all party games.
If you look at the rules queries for Taboo on BGG there are lots with 'Dispute' in the title.   Its a fun silly game and not worth a dispute about, Don't let the rules get in the way of just enjoying playing.