Honest blonde! (4)
I believe the answer is:
fair
This clue is a double definition.
'honest' is the first definition.
(I've seen this before)
'blonde' is the second definition.
('fair' can be similar in meaning to 'blonde')
(Other definitions for fair that I've seen before include "Just treatment of others" , "Moderately good; blonde" , "Having light-coloured hair and skin" , "Equitable ? - trade show" , "Just; amusement" .)