Nothing more than a lake (4)

I believe the answer is:

mere

I believe this is a double definition.

'nothing more than' is the first definition.
(I've seen this before)

'a lake' is the second definition.
(I know that mere is a type of pond)

(Other definitions for mere that I've seen before include "Nothing more than - water" , "Insignificant" , "Lake (poetic); Maori war club" , "Pierre's mother identified" , "of no significance" .)

I've seen this clue in The Irish Independent.

Want a hint initially instead of a full solution? Install my app