Row involving Dr Wood (6)
I believe the answer is:
timber
'wood' is the definition.
(thesaurus)
'row involving dr' is the wordplay.
'row' becomes 'tier' (tier is a kind of row).
'involving' means one lot of letters goes inside another.
'dr' becomes 'mb' (both can mean doctor).
'tier' placed around 'mb' is 'TIMBER'.
(Other definitions for timber that I've seen before include "Lumberjack's warning call" , "Sawn wood" , "Tree-feller's cry" , "board" , "Watch out for falling tree!" .)