Degenerative state of Venetian magistrate keeping volunteer army once (6)
I believe the answer is:
dotage
'degenerative state' is the definition.
(dotage is getting elderly or senile)
'venetian magistrate keeping volunteer army once' is the wordplay.
I cannot really understand how this works, but
'volunteer' could be 'ta' (member of the Territorial Army, volunteer regiment) and 'ta' is present in the answer.
'magistrate' could be 'doge' (doge is a kind of magistrate) and 'doge' is found within the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
'of' acts as a link.
Can you help me to learn more?
(Other definitions for dotage that I've seen before include "In which one would be old and weak" , "Mental infirmity in old age" , "Later life, when old and weak" , "Foolish infatuation" , "Feeble-minded period late in life" .)