Gathering there’s no end of damage on tunic (7)
I believe the answer is:
harvest
'gathering' is the definition.
(I know that harvest is a type of gathering)
'no end of damage on tunic' is the wordplay.
'no end of' means to remove the last letter.
'damage' becomes 'harm' (synonyms).
'on' means one lot of letters go next to another.
'tunic' becomes 'vest'.
'harm' with its final letter removed is 'har'.
'har'+'vest'='HARVEST'
'there's' acts as a link.
(Other definitions for harvest that I've seen before include "reap rewards" , "Crop gathering" , "Produce" , "Cut down" , "Crops gathered in" .)