He damaged, at the Victoria and Albert, a number (6)
I believe the answer is:
vandal
'he damaged at the victoria' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'and albert a number' is the wordplay.
I cannot quite see how this works, but
an anagram of 'and' is 'nda' which is located in the answer.
'albert' could be 'al' and 'al' is present in the answer.
'number' could be 'v' (V is an example) and 'v' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for vandal that I've seen before include "Someone who destroys or defaces property" , "One doing deliberate damage" , "One who maliciously causes damage" , "Someone who wilfully damages property" , "Old German" .)