25) If something is cut it has been ????, particularly wooden items, (the N is correct) then move the first letter (an S) to the end.
24 I have already given you a hint on this, and your first wild guess is correct.
29 is unclued and you need to consult Chambers for the answer, it is thematic.
13d is an anagram, consult Chambers to confirm
21 Correct, but again I hinted on this before.
36a not as you have surmised, 26d is also what you use to connect pieces of paper together.