Increased force, worn out (5)
I believe the answer is:
grown
'increased' is the definition.
(I've seen this before)
'force worn out' is the wordplay.
'force' becomes 'g' (short for gravity).
'out' is an anagram indicator (out can mean wrong or inaccurate).
'worn' is an anagram of 'rown'.
'g'+'rown'='GROWN'
(Other definitions for grown that I've seen before include "Big" , "Cultivated" , "Increased; developed" , "Matured" , "increased in stature?" .)