Worker oddly ignored hernia to secure new aerial (7)
I believe the answer is:
antenna
'aerial' is the definition.
(I know that aerial can be written as antenna)
'worker oddly ignored hernia to secure new' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'oddly ignored' indicates alternate letters (letters in odd-numbered positions are removed).
'to secure' is an insertion indicator (inserted letters are secured inside).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
The alternating letters of 'hernia' are 'ena'.
'ena' enclosing 'n' is 'enna'.
'ant'+'enna'='ANTENNA'
(Other definitions for antenna that I've seen before include "Insect's feeler" , "Transmitting aerial" , "connected to 41?" , "sensitive feeler" , "Insect's sensory appendage" .)