Happy to accept son is dependable (10)
I believe the answer is:
consistent
'dependable' is the definition.
(thesaurus)
'happy to accept son is' is the wordplay.
'happy' becomes 'content' ('content' is associated in meaning with 'happy'**).
'to accept' is an insertion indicator.
'son' becomes 's'.
's'+'is'='sis'
'content' going around 'sis' is 'CONSISTENT'.
(Other definitions for consistent that I've seen before include "true to principles" , "uniform" , "compatible" , "in agreement" , "Unchanging in standard over time" .)