Corroborate representation of nun with pride (8)
I believe the answer is:
underpin
'corroborate' is the definition.
(I know that corroborate can be written as underpin)
'representation of nun with pride' is the wordplay.
'representation of' indicates anagramming the letters (I've seen this in other clues).
'with' means one lot of letters go next to another.
'nun'+'pride'='nunpride'
'nunpride' anagrammed gives 'UNDERPIN'.
(Other definitions for underpin that I've seen before include "corroborate" , "Form the basis for" , "Support or strengthen from beneath" , "Prop up with nun pride" , "buttress" .)