Tablet unfortunately crushed in field (12)
I believe the answer is:
battleground
'field' is the definition.
('battleground' can be a synonym of 'field')
'tablet unfortunately crushed' is the wordplay.
'unfortunately' is an anagram indicator.
'crushed' becomes 'ground' ('ground' can be a synonym of 'crushed').
'tablet' is an anagram of 'battle'.
'battle'+'ground'='BATTLEGROUND'
'in' acts as a link.
(Other definitions for battleground that I've seen before include "scene of conflict" , "Area of conflict" , "arena" , "Place of military encounter" , "Army hospital near here perhaps" .)