Paint bird and lions roaming (8)
I believe the answer is:
emulsion
'paint' is the definition.
(I've seen this before)
'bird and lions roaming' is the wordplay.
'bird' becomes 'emu' (emu is a kind of bird).
'and' says to put letters next to each other.
'roaming' indicates an anagram.
'lions' with letters rearranged gives 'lsion'.
'emu'+'lsion'='EMULSION'
(Other definitions for emulsion that I've seen before include "Wall paint" , "Type of paint" , "Mixture of insoluble liquids" , "Mixture involving two liquids which do not readily combine" .)