Conservative with tender for treasury (6)
I believe the answer is:
coffer
'treasury' is the definition.
(thesaurus)
'conservative with tender' is the wordplay.
'conservative with' becomes 'c' (I can't justify this - if you can you should give a lot more credence to this answer).
'tender' becomes 'offer' ('offer' can be a synonym of 'tender').
'c'+'offer'='COFFER'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for coffer that I've seen before include "safe" , "Strongbox" , "Treasure chest" , "Strong box at the treasury" , "Small chest for keeping valuables" .)