Unable to catch fast doe running without delay inside (4,2,1,4)
I believe the answer is:
deaf as a post
'unable to catch' is the definition.
(unable to hear or catch things)
'fast doe running without delay inside' is the wordplay.
'running' indicates anagramming the letters (the letters run around to different places).
'without delay' becomes 'ASAP' (as soon as possible).
'inside' means one lot of letters goes inside another.
'fast'+'doe'='fastdoe'
'fastdoe' is an anagram of 'deafost'.
'deafost' placed around 'asap' is 'DEAF AS A POST'.
(Another definition for deaf as a post that I've seen is " Extremely hard of hearing".)