Is upset, putting on gardener’s unknown stockings? (7)
I believe the answer is:
hosiery
'stockings?' is the definition.
(I've seen this in another clue)
'is upset putting on gardener's unknown' is the wordplay.
'upset' is an anagram indicator.
'putting on' indicates putting letters inside (some letters wear or 'put on' others).
'gardener' becomes 'hoer' (I've seen this before).
'unknown' becomes 'y' (algebra).
'is' with letters rearranged gives 'si'.
'si' put inside 'hoer' is 'hosier'.
'hosier'+'y'='HOSIERY'
(Other definitions for hosiery that I've seen before include "Tights and the like" , "the object of much leg-pulling" , "intimate this?" , "Socks, stockings and tights" , "Underwear items such as stockings" .)