Gather grass on school store (4,4)
I believe the answer is:
tuck shop
'school store' is the definition.
'tuck-shop' can be an answer for 'store' (tuck-shop is a kind of store). I'm not sure about the 'school' bit.
'gather grass' is the wordplay.
'gather' becomes 'tuck' (synonyms).
'grass' becomes 'shop' (I've seen this before).
'tuck'+'shop'='TUCK-SHOP'
'on' acts as a link.
Can you help me to learn more?
(Other definitions for tuck shop that I've seen before include "Charterhouse store" , "Candy store for schoolchildren" , "Where schoolchildren buy sweets" , "what caters for kids" , "(School) snacks seller" .)