Caught fungal infection scratching backside, with your pen essentially inserted - that's embarrassing (12)
I believe the answer is:
cringeworthy
'embarrassing' is the definition.
(I've seen this before)
'caught fungal infection scratching backside with your pen essentially inserted' is the wordplay.
I cannot really see how this works, but
'caught' could be 'c' (cricket abbreviation) and 'c' is found within the answer.
'with' could be 'w' (abbreviation) and 'w' is found in the answer.
'your' could be 'thy' (I've seen this before) and 'thy' is located in the answer.
This explanation may well be incorrect...
'that's' acts as a link.
(Other definitions for cringeworthy that I've seen before include "Acutely embarrassing" , "Causing embarrassment" , "Severely embarrassing" .)