Glaring mistake identifying monkey (6)
I believe the answer is:
howler
This clue is a double definition.
'glaring mistake' is the first definition.
(I've seen this before)
'monkey' is the second definition.
(I know that howler is a type of monkey)
'identifying' acts as a link.
(Other definitions for howler that I've seen before include "5 in 9 29 [REVEREND IN CHARLES DICKENS]" , "A foolish mistake, sounds noisy" , "Serious avoidable mistake" , "Stupid glaring mistake" , "Serious blunder" .)