Following, with a beating heart, in terrible fear (5)
I believe the answer is:
after
'following' is the definition.
(thesaurus)
'a beating heart in terrible fear' is the wordplay.
'heart' says to take the centre.
'in' means one lot of letters goes inside another.
'terrible' indicates an anagram.
The central letter of 'beating' is 't'.
'fear' is an anagram of 'afer'.
't' placed inside 'afer' is 'AFTER'.
'with' is the link.
(Other definitions for after that I've seen before include "back along > deck" , "In honour of" , "Subsequently" , "Following, consequent to" , "since" .)