Indeed, writer taking drug became more profound (8)
I believe the answer is:
deepened
'became more profound' is the definition.
(I've seen this before)
'indeed writer taking drug' is the wordplay.
I cannot quite understand how this works, but
'writer' could be 'ed' (I've seen this in other clues) and 'ed' is found in the answer.
'drug' could be 'e' (e is another name for ecstasy) and 'e' is present in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for deepened that I've seen before include "Made more intense" , "Made more profound" , "Became more profound" .)