Teased mercilessly when in tatters (6)
I believe the answer is:
ragged
This clue could be a double definition.
'teased mercilessly' is the first definition.
'ragged' can be an answer for 'teased' ('rag' can be a synonym of 'tease'). I am not sure about the 'mercilessly' bit.
'in tatters' is the second definition.
(I've seen this in another clue)
'when' is the link.
Can you help me to learn more?
(Other definitions for ragged that I've seen before include "Teased; untidy; badly dressed" , "being poorly dressed" , "Shabby" , "Played practical jokes - in tatters" , "Threadbare" .)