Heavy study, following field (6)
I believe the answer is:
leaden
'heavy' is the definition.
(I know that heavy can be written as leaden)
'study following field' is the wordplay.
'study' becomes 'den' (term for a study or office).
'following' says to put letters next to each other.
'field' becomes 'lea' (lea can mean a meadow or field of grass).
'den' after 'lea' is 'LEADEN'.
(Other definitions for leaden that I've seen before include "Gloomy - slow-moving" , "Slow-moving, being like heavy metal" , "Heavy or slow, like dark-gray metal" , "Heavy and slow, as if weighted down with heavy metal" , "Heavy - plodding" .)