Spot conservationists with a primary food supplier (8)
I believe the answer is:
placenta
'primary food supplier' is the definition.
(a placenta provides food to a baby in the womb)
'spot conservationists with a' is the wordplay.
'spot' becomes 'place' (synonyms).
'conservationists' becomes 'NT' (abbreviation for National Trust).
'with' means one lot of letters go next to another.
'place'+'nt'+'a'='PLACENTA'
(Other definitions for placenta that I've seen before include "Organ feeding a foetus" , "21 that feeds the embryo" , "temporary organ" , "baby food" , "Plate can appear in organ in womb during pregnancy" .)