Miss out about a fellow's apes (7)

'apes' is the definition.
(I've seen this in another clue)

'miss out about a fellow's' is the wordplay.
'out' means to remove the last letter.
'about' shows that the letters should be reversed in order.
'a fellow's' becomes 'ians' (common masculine name).
'miss' with its last letter taken away is 'mis'.
'mis' in reverse letter order is 'sim'.
'sim'+'ians'='SIMIANS'