Dishy estate agent is secretly most timid (6)
I believe the answer is:
shyest
'most timid' is the definition.
(I've seen this before)
'dishy estate agent is secretly' is the wordplay.
'is secretly' indicates the answer is hidden within the clue.
'SHYEST' is hidden within 'dishy estate agent'.
(Other definitions for shyest that I've seen before include "Most bashful or self-conscious" , "Most diffident" , "withdrawn the most" , "Most reticent" , "Most timid" .)