Incompetent psychiatrist entered, not getting less? (12)
I believe the answer is:
unshrinkable
'not getting less?' is the definition.
I can't judge whether this definition defines the answer.
'incompetent psychiatrist entered' is the wordplay.
'incompetent' becomes 'unable' (I've seen this before).
'psychiatrist' becomes 'shrink' (informal term for a psychiatrist).
'entered' indicates putting letters inside.
'unable' enclosing 'shrink' is 'UNSHRINKABLE'.
Can you help me to learn more?
(Another definition for unshrinkable that I've seen is " (Of fabric) retaining its size".)