Having trouble parsing these, help appreciated.....
13a Heard a line twist in tighter corner (5,5) - ACUTE ANGLE (Corner)
14d Exact changes heard originally on good authority (2,8) - EX CATHEDRA (On good authority)
This is an anagram of EXACT and HEARD, but because the anagram indicator, 'Changes', comes in between the words and 'Heard' is followed by 'Originally', I think there's more to it - but I can't see what.