Little monkey, almost tame, ran freely round one (7)
I believe the answer is:
tamarin
'little monkey' is the definition.
(tamarin is a type of monkey)
'almost tame ran freely round one' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'freely' indicates anagramming the letters.
'round' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'tame' with its last letter taken off is 'tam'.
'ran' with letters rearranged gives 'arn'.
'arn' placed around 'i' is 'arin'.
'tam'+'arin'='TAMARIN'
(Other definitions for tamarin that I've seen before include "Main art (anag) - monkey" , "Small monkey of the marmoset family" .)