Small tablet found in shed (5)
I believe the answer is:
spill
'shed' is the definition.
(I know that shed can be written as spill)
'small tablet' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'tablet' becomes 'pill' (synonyms).
's'+'pill'='SPILL'
'found in' acts as a link.
(Other definitions for spill that I've seen before include "Thin piece of wood or rolled paper to light a fire" , "Thin piece of wood used to light a fire" , "Shed" , "Overturn" , "Taper; slop" .)