Send back mushrooms starter, oddly lacking vision (7)
I believe the answer is:
spectre
'lacking vision' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'send back mushrooms starter oddly' is the wordplay.
'send back' says the letters should be written backwards.
'mushrooms' becomes 'ceps' (cep is a type of mushroom).
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
The alternating letters of 'starter' are 'tre'.
'ceps' in reverse letter order is 'spec'.
'spec'+'tre'='SPECTRE'
Can you help me to learn more?
(Other definitions for spectre that I've seen before include "after-image?" , "Enemy organisation for James Bond; ghost" , "Ghostly figure" , "Respect for a ghost" , "spirit" .)