New bug going round, caught in gym with child (8)
I believe the answer is:
pregnant
'with child' is the definition.
(similar in meaning)
'new bug going round caught in gym' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'bug' becomes 'anger' (both can mean to annoy).
'going round' says the letters should be written in reverse.
'caught in' indicates putting letters inside.
'gym' becomes 'PT' (Physical Training).
'n'+'anger'='nanger'
'nanger' written backwards gives 'regnan'.
'regnan' inserted within 'pt' is 'PREGNANT'.
(Other definitions for pregnant that I've seen before include "Expecting a child" , "With child, enceinte" , "full of implications" , "Gravid" , "loaded" .)