Harms layout of bog (5)
I believe the answer is:
marsh
'bog' is the definition.
(I've seen this in another clue)
'harms layout' is the wordplay.
'layout' is an anagram indicator (an alternative layout of the letters).
'harms' with letters rearranged gives 'MARSH'.
'of' acts as a link.
(Other definitions for marsh that I've seen before include "Fen" , "Waterlogged land" , "eg Romney" , "Wetland" , "Bog, swamp" .)