It's used in seasoning sausages (4)
I believe the answer is:
sage
'seasoning sausages' is the definition.
'sage' can be an answer for 'seasoning' (I've seen this in another clue). I am unsure of the 'sausages' bit.
'it's used' is the wordplay.
'it' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'used' becomes 'ge' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sa'+'ge'='SAGE'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for sage that I've seen before include "Clary" , "Wise man - flavoursome plant" , "Herb used in cooking" , "philosopher" , "Learned" .)