Prefers internal attribute (5)
I believe the answer is:
refer
'attribute' is the definition.
(I've seen this in another clue)
'prefers internal' is the wordplay.
'internal' says the answer is hidden in the clue.
'REFER' can be found hidden inside 'prefers'.
(Other definitions for refer that I've seen before include "Fail (an exam candidate)" , "Send or direct to a specialist" , "Hand over for consideration (to)" , "Mention, cite" , "Send a patient to a specialist" .)