What bit possibly can be over by Thursday? (5)
I believe the answer is:
tooth
'what bit possibly can' is the definition.
I can't tell whether this definition defines the answer.
'over by thursday?' is the wordplay.
'over' becomes 'too' (I've seen this before).
'by' means one lot of letters go next to another.
'thursday?' becomes 'Th' (common abbreviation).
'too'+'th'='TOOTH'
'be' is the link.
Can you help me to learn more?
(Other definitions for tooth that I've seen before include "It erupts" , "Let it stand" , "Taste" , "Chopper" , "Gearwheel cog" .)