Spice found on summits of unusual mountains all in South Carolina (5)
I believe the answer is:
sumac
'spice' is the definition.
(I've seen this before)
'on summits of unusual mountains all in south carolina' is the wordplay.
'on' is an insertion indicator (as in clothing \'on\' a person).
'summits of' suggests taking the first letters (I've seen 'summit of' mean this).
'mountains all' becomes 'ma' (this might be a standard abbreviation I've not previously seen).
'in' is an insertion indicator.
'south carolina' becomes 'sc'.
The initial letter of 'unusual' is 'u'.
'ma' placed into 'sc' is 'smac'.
'u' going inside 'smac' is 'SUMAC'.
'found' is the link.
Can you help me to learn more?
(Other definitions for sumac that I've seen before include "Shrub bright in autumn" , "purchase from garden centre?" , "Novelist" , "Rudely brief" , "Tree colourful in autumn" .)