Only a lake (4)

I believe the answer is:

mere

I believe this is a double definition.

'only' is the first definition.
(I've seen this in another clue)

'a lake' is the second definition.
(mere is a kind of lake)

(Other definitions for mere that I've seen before include "Pond - pure and simple" , "Lake in Cumbria" , "Paltry" , "Small area of standing water" , "Lake (and nothing else?)" .)

I've seen this clue in The Times, The Irish Independent, The Mirror and The Sun.

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