Robert gets out for 50 – or a duck! (4)
I believe the answer is:
blob
'a duck' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'robert gets out for 50' is the wordplay.
'robert' becomes 'bob' (I've seen this before).
'gets' indicates putting letters inside (gets can mean captures or absorbs).
'out for 50' becomes 'l' (I can't justify this - if you can you should believe this answer much more).
'bob' enclosing 'l' is 'BLOB'.
'or' acts as a link.
Can you help me to learn more?
(Other definitions for blob that I've seen before include "Drop of thick liquid or viscous substance" , "Small piece signifying nothing" , "Globule; round spot" , "Indistinct shape" , "Indeterminate mass" .)