Qualified professionals in study sit up when presented with edgy thesis (8)
I believe the answer is:
dentists
'qualified professionals' is the definition.
'dentists' can be an answer for 'professionals' (dentist is a kind of professional). I am unsure of the 'qualified' bit.
'study sit up when presented with edgy thesis' is the wordplay.
'study' becomes 'den' (term for a study or office).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'when presented with edgy thesis' becomes 'ts' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sit' back-to-front is 'tis'.
'den'+'tis'+'ts'='DENTISTS'
'in' is the link.
Can you help me to learn more?
(Other definitions for dentists that I've seen before include "Professional carers for teeth" , "Tooth doctors" , "Orthodontists, periodontists etc." , "They care for teeth" .)