Have completed (I think) but am either going mad or there is (again!) some sloppy clueing going on here...
18a - amazed at fat steed - brag outrageously (13)
I have 'flabbergasted'.
The clue seems to indicate an anagram of 'fat steed brag' but is one letter short and even if it included an 'L'; maybe 'flat' rather than 'fat' to make the 13 letters it still wouldn't work as an anagram; too may Ts, not enough Bs.
Have I lost the plot?????