Pretty as you can imagine (5)
I believe the answer is:
fancy
'imagine' is the definition.
(I know that fancy is a more specific form of the action imagine)
'pretty as you can' is the wordplay.
I cannot really understand how this works, but
an anagram of 'can' is 'anc' which is located in the answer.
The remaining letters 'fy' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for fancy that I've seen before include "Imagine - whim - highly decorated" , "Elaborate; whim" , "Be crazy about" , "Imagine - find attractive" , "An ornamental whim?" .)