Belonging to base we use frequently (5)
I believe the answer is:
often
'frequently' is the definition.
(synonyms)
'belonging to base' is the wordplay.
'belonging to' becomes 'of' ('of' can mean 'belonging to' or 'owned by').
'base' becomes 'ten' (I have seen 'Decimal base ' mean 'ten' so perhaps 'base' could also mean 'ten').
'of'+'ten'='OFTEN'
'we use' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for often that I've seen before include "on many occasions" , "Repeatedly, many times" , "Frequently, habitually" , "Repeatedly with regularity" , "A lot" .)