Hard worker, say, follows architect (7)
I believe the answer is:
adamant
'hard' is the definition.
(I've seen this before)
'worker say follows architect' is the wordplay.
'worker say' becomes 'ant' (worker is a type of ant).
'follows' means one lot of letters go next to another.
'architect' becomes 'adam' (I've seen this before).
'ant' after 'adam' is 'ADAMANT'.
(Other definitions for adamant that I've seen before include "unshakeable in purpose" , "Unpersuadable" , "Insistent, inflexible" , "uncompromising" , "Unyielding, won't change mind" .)