No more than a pond (4)
I believe the answer is:
mere
I believe this clue is a double definition.
'no more than' is the first definition.
(I've seen this before)
'a pond' is the second definition.
(mere is a kind of pond)
(Other definitions for mere that I've seen before include "Pond - pure and simple" , "Lake (poetic); Maori war club" , "of no significance" , "See 13" , "Lake; simple" .)