I am bringing boy round, a simple fellow (5)
I believe the answer is:
simon
'a simple fellow' is the definition.
(as in the nursery rhyme character Simple Simon)
'i am bringing boy round' is the wordplay.
'i am' becomes 'I'm' (contraction).
'bringing boy' becomes 'son' (I am not sure about this - if you are sure you should believe this answer much more).
'round' means one lot of letters goes inside another.
'im' put into 'son' is 'SIMON'.
Can you help me to learn more?
(Other definitions for simon that I've seen before include "- and Garfunkel" , "Fellow" , "Sir -- Rattle, conductor" , "he says it's a game" , "Simple pieman" .)