Length of time in post — years in a decade, you’re talking! (6)
I believe the answer is:
tenure
'length of time' is the definition.
'tenure' can be an answer for 'time' (thesaurus). I'm unsure of the 'length of' bit.
'post years in a decade you're talking' is the wordplay.
I cannot really understand how this works, but
'decade' could be 'ten' (synonyms) and 'ten' is found within the answer.
The remaining letters 'ure' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'in' is the link.
Can you help me to learn more?
(Other definitions for tenure that I've seen before include "Term for which to hold a position" , "Right to keep job" , "Permanent employment right" , "Residence" , "Dairy product" .)