Writers I have taken to be thoughtful (7)
I believe the answer is:
pensive
'thoughtful' is the definition.
(similar in meaning)
'writers i have taken to' is the wordplay.
'writers' becomes 'pens' (writing implements).
'i have' becomes 'I've' (contraction of 'I have').
'taken to' says to put letters next to each other.
'pens'+'ive'='PENSIVE'
'be' acts as a link.
(Other definitions for pensive that I've seen before include "Introspective, maybe moody" , "in a brown study?" , "musing" , "Engaged in deep thought" , "Deeply thoughtful" .)