Dependable and firm, moment one departs (8)
I believe the answer is:
constant
'dependable' is the definition.
(thesaurus)
'and firm moment one departs' is the wordplay.
I cannot really see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is found within the answer.
'firm' could be 'co' (a firm is a company) and 'co' is found in the answer.
'moment' could be 's' and 's' is present in the answer.
'one' could be 'an' (I've seen this in other clues) and 'an' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for constant that I've seen before include "exactly as before" , "Resolute" , "without changes" , "Remaining the same" , "Endless" .)