Burdensome or laboured field study (6)
I believe the answer is:
leaden
'burdensome' is the definition.
(thesaurus)
'laboured field study' is the wordplay.
'laboured field' becomes 'lea' (lea can mean a meadow or field of grass. I am not sure about the 'laboured' bit.).
'study' becomes 'den' (term for a study or office).
'lea'+'den'='LEADEN'
'or' is the link.
Can you help me to learn more?
(Other definitions for leaden that I've seen before include "Depressing - heavy" , "Heavy and slow, as if weighted down with heavy metal" , "Describes grey overcast skies" , "Heavy or slow, like dark-gray metal" , "Oppressive" .)