Darned watch includes week and day (5)
I believe the answer is:
sewed
'darned' is the definition.
(I've seen this before)
'watch includes week and day' is the wordplay.
'watch' becomes 'see' (seeing is a kind of watching).
'includes' is an insertion indicator.
'week' becomes 'w' (abbreviation).
'and' means one lot of letters go next to another.
'day' becomes 'd'.
'see' going around 'w' is 'sewe'.
'sewe'+'d'='SEWED'
(Other definitions for sewed that I've seen before include "Used needle and thread" , "Joined" , "Did needlework" , "Fastened with thread" , "Darned" .)