Irregular route skirting cape close to Whitby (6)
I believe the answer is:
patchy
'irregular' is the definition.
(I've seen this before)
'route skirting cape close to whitby' is the wordplay.
'route' becomes 'path' (synonyms).
'skirting' means one lot of letters goes inside another.
'cape' becomes 'c' (abbreviation used on maps).
'close to' says to take the final letters (the close/ending of).
The final letter of 'whitby' is 'y'.
'path' going around 'c' is 'patch'.
'patch'+'y'='PATCHY'
(Other definitions for patchy that I've seen before include "Often repaired" , "Uneven in quality like repaired clothes" , "Inconsistent" , "Uneven in quality - mended too often" , "Irregular or uneven" .)