Sketch duck until flying to end of lake (7)
I believe the answer is:
outline
'sketch' is the definition.
(synonyms)
'duck until flying to end of lake' is the wordplay.
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'flying' indicates an anagram (letters fly around into new positions).
'to end of' indicates one should take the final letters.
The last letter of 'lake' is 'e'.
'until' is an anagram of 'utlin'.
'o'+'utlin'+'e'='OUTLINE'
(Other definitions for outline that I've seen before include "Synopsis -- silhouette" , "(Give) schematic account" , "Sketch, skeleton" , "Give a summary of" , "Sketch or contour" .)