Low tide (4)
I believe the answer is:
neap
'low tide' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for neap that I've seen before include "Tide sketched by a pen" , "Tide with least fall and rise of water" , "Of smallest tidal range" , "Tide when there is the least variation between high and low water" , "Least in difference between high and low tides" .)