Forty per cent of farms fit to be termed fertile (6)
I believe the answer is:
arable
'fertile' is the definition.
(I've seen this in another clue)
'forty per cent of farms fit to be termed' is the wordplay.
I cannot quite understand how this works, but
'per' could be 'a' and 'a' is present in the answer.
'fit' could be 'able' (similar in meaning) and 'able' is found within the answer.
A single letter 'r' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for arable that I've seen before include "agricultural land" , "Suitable for farming" , "Of land, capable of growing crops" , "(Of land) able to be cultivated" , "Tillable" .)