Thoughtful enclosures I have seen (7)
I believe the answer is:
pensive
'thoughtful' is the definition.
(similar in meaning)
'enclosures i have seen' is the wordplay.
'enclosures' becomes 'pens' (pen is a kind of enclosure).
'have' means one lot of letters go next to another.
'seen' becomes 've' (I can't justify this - if you can you should believe this answer much more).
'pens'+'i'+'ve'='PENSIVE'
Can you help me to learn more?
(Other definitions for pensive that I've seen before include "Thinking deeply" , "Brooding" , "Meditative" , "musing" , "Introspective, maybe moody" .)