Suggestion corps in error will have to work on farm area (9)
I believe the answer is:
scintilla
'suggestion' is the definition.
(thesaurus)
'corps in error will have to work on farm area' is the wordplay.
'corps' becomes 'C' (military abbreviation for corps).
'in error' becomes 'sin' (I can't explain this - if you can you should give a lot more credence to this answer).
'will have' is an insertion indicator (have can mean to hold or contain).
'to work on farm' becomes 'till' (I've seen this before).
'area' becomes 'a' (maths abbreviation).
'c' placed within 'sin' is 'scin'.
'scin'+'till'+'a'='SCINTILLA'
Can you help me to learn more?
(Other definitions for scintilla that I've seen before include "suspicion" , "Tiny, scarcely detectable amount" , "flash" , "The smallest amount" , "A tiny bit" .)