Monkeys developed scars around nails intermittently (7)
I believe the answer is:
rascals
'monkeys' is the definition.
('rascal' can be a synonym of 'monkey')
'developed scars around nails intermittently' is the wordplay.
'developed' indicates an anagram.
'around' means one lot of letters goes inside another.
'intermittently' indicates alternate letters.
The alternate letters of 'nails' are 'al'.
'scars' with letters rearranged gives 'rascs'.
'rascs' enclosing 'al' is 'RASCALS'.
(Other definitions for rascals that I've seen before include "Scoundrels or naughty children" , "Knaves" , "monkeys" , "Mischievous children" , "Mischievous or cheeky people" .)