Light yellow bog, loose inside (6)
I believe the answer is:
flaxen
'light yellow' is the definition.
(I've seen this before)
'bog loose inside' is the wordplay.
'bog' becomes 'fen' (I've seen this in another clue).
'loose' becomes 'lax' (associated in meaning).
'inside' is an insertion indicator.
'fen' going around 'lax' is 'FLAXEN'.
(Other definitions for flaxen that I've seen before include "Pale yellow, as hair may be" , "Of a particular plant fibre" , "Pale yellow in colour" , "Light yellow" , "Blonde, reading poetry" .)