Danger of a laundry detergent completely fading a little shirt (5)
I believe the answer is:
'danger' is the definition.
'a laundry detergent completely fading a little shirt' is the wordplay.
I cannot quite see how this works, but
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is present in the answer.
'little' could be 'l' (abbreviation for little) and 'l' is found in the answer.
A single letter 'i' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'of' is the link.
(Other definitions for peril that I've seen before include "Danger of serious kind" , "Hazardous situation" , "Quest" , "Immediate danger" , "risk" .)