Like some paint floating in pond across river (7)
I believe the answer is:
nondrip
'like some paint' is the definition.
'floating in pond across river' is the wordplay.
'floating' indicates anagramming the letters (float can mean fluctuate or oscillate).
'across' indicates putting letters inside.
'river' becomes 'r'.
'in'+'pond'='inpond'
'inpond' with letters rearranged gives 'nondip'.
'nondip' placed around 'r' is 'NONDRIP'.
(Other definitions for nondrip that I've seen before include "Thixotropic (paint)" , "Sort of paint" , "(Of paint) not running" , "Thick type of paint" , "depiction of 13 [HERO], presumably" .)