Disaster as teacher turns up with lace undone (7)
I believe the answer is:
debacle
'disaster' is the definition.
(synonyms)
'teacher turns up with lace undone' is the wordplay.
'teacher' becomes 'BEd' (Bachelor of Education).
'turns up' says the letters should be written in reverse.
'with' is a charade indicator (letters next to each other).
'undone' indicates an anagram.
'bed' back-to-front is 'deb'.
'lace' with letters rearranged gives 'acle'.
'deb'+'acle'='DEBACLE'
'as' is the link.
(Other definitions for debacle that I've seen before include "A sound defeat" , "great failure" , "A complete collapse or messy failure" , "Disatrous collapse" , "Catastrophe" .)