Dull and tedious day with parent (5)
I believe the answer is:
drear
'dull and tedious' is the definition.
(I've seen this before)
'day with parent' is the wordplay.
'day' becomes 'd' (abbreviation for day).
'with' says to put letters next to each other.
'parent' becomes 'rear' (synonyms).
'd'+'rear'='DREAR'
(Other definitions for drear that I've seen before include "Gloomy and cheerless" , "Morose" , "gloomy in poem" , "Depressingly dull" , "grave" .)