Strictly speaking, not busily following an articulated truck (7)
I believe the answer is:
rigidly
'strictly' is the definition.
(thesaurus)
'not busily following an articulated truck' is the wordplay.
'not busily' becomes 'idly' (idle is the opposite of busy).
'following' means one lot of letters go next to another.
'an articulated truck' becomes 'rig' (I've seen this in another clue. I am not sure about the 'articulated' bit.).
'idly' after 'rig' is 'RIGIDLY'.
'speaking' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for rigidly that I've seen before include "in unyielding grip" , "without bending" , "Stiffly" .)