Two couches, a uniform between them smeared (8)
I believe the answer is:
bedaubed
'smeared' is the definition.
('bedaub' can be a synonym of 'smear')
'two couches a uniform between them' is the wordplay.
'two couches' can mean two replacements for 'couch'.
'couch' becomes 'bed' (I've seen this before).
'couch' becomes 'bed' (I've seen this before).
'uniform' becomes 'U' (phonetic alphabet: alpha, bravo, charlie etc.).
'between them' means one lot of letters goes inside another.
'a'+'u'='au'
'bed'+'bed'='bedbed'
'bedbed' placed around 'au' is 'BEDAUBED'.
(Other definitions for bedaubed that I've seen before include "Covered with splashes" , "thickly coated" .)