Get mail perhaps but not without delay (4,3)
I believe the answer is:
time lag
'delay' is the definition.
(a time lag is a delay)
'get mail perhaps' is the wordplay.
'perhaps' is an anagram indicator.
'get'+'mail'='getmail'
'getmail' is an anagram of 'TIME-LAG'.
'but not without' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for time lag that I've seen before include "Gap between linked events" , "interval" , "Delay" .)