Gathering container, go off to collect first of gooseberries (12)
I believe the answer is:
congregation
'gathering' is the definition.
(congregation is a kind of gathering)
'container go off to collect first of gooseberries' is the wordplay.
'off' indicates anagramming the letters.
'to collect' means one lot of letters goes inside another.
'first of' suggests taking the first letters.
The initial letter of 'gooseberries' is 'g'.
'container'+'go'='containergo'
'containergo' with letters rearranged gives 'conregation'.
'conregation' going around 'g' is 'CONGREGATION'.
(Other definitions for congregation that I've seen before include "Group of worshippers" , "Group assembling for worship" .)