Right behind tablet, a column (6)
I believe the answer is:
pillar
'column' is the definition.
(both can mean an upright structure)
'right behind tablet a' is the wordplay.
'right' becomes 'r' (common abbreviation).
'behind' says to put letters next to each other.
'tablet' becomes 'pill' (synonyms).
'pill'+'a'='pilla'
'r' after 'pilla' is 'PILLAR'.
(Other definitions for pillar that I've seen before include "Stylite would live on it" , "Upright column" , "Tall support" , "Building support" , "Architectural support" .)