Type of farm horse, outwardly lame (6)
I believe the answer is:
arable
'type of farm' is the definition.
'arable' can be an answer for 'farm' (thesaurus). I am not certain of the 'type of' bit.
'horse outwardly lame' is the wordplay.
'horse' becomes 'arab' (Arab is a type of horse).
'outwardly' says to hollow out the word (remove centre letters) (only the outermost letters are used).
'lame' with its middle taken out is 'le'.
'arab'+'le'='ARABLE'
Can you help me to learn more?
(Other definitions for arable that I've seen before include "farming land!" , "Of land, fit to be cultivated" , "(Of land) able to be cultivated" , "Of land, fit for cultivation" , "Suitable for farming" .)