Possibly firm foundation (13)
I believe the answer is:
establishment
This clue might be a double definition.
'possibly firm' is the first definition.
'establishment' can be an answer for 'firm' (thesaurus). I am unsure of the 'possibly' bit.
'foundation' is the second definition.
(I've seen this before)
Can you help me to learn more?
(Other definitions for establishment that I've seen before include "Those in power" , "Institution; (the) ruling classes" , "system" , "Action of setting up on a permanent basis" , "Power-holding class" .)