Model turns up hugging brown giants (6)
I believe the answer is:
titans
'giants' is the definition.
('titan' can be a synonym of 'giant')
'model turns up hugging brown' is the wordplay.
'model' becomes 'sit' ('sit' can be a synonym of 'model'**).
'turns up' shows that the letters should be reversed in order.
'hugging' means one lot of letters goes inside another.
'brown' becomes 'tan' (tan is a kind of brown).
'sit' backwards is 'tis'.
'tis' placed around 'tan' is 'TITANS'.
(Other definitions for titans that I've seen before include "Legendary giants with taints" , "Taints found in great men" , "Old Greek gods, very strong like Atlas" , "Big fellows" , "Giant gods of Greek mythology" .)