Forth river bridges do well (6)
I believe the answer is:
thrive
'do well' is the definition.
(to thrive is to succeed or develop well)
'forth river bridges' is the wordplay.
'THRIVE' is hidden in amongst the letters.
However, I'm not sure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for thrive that I've seen before include "Prosper, grow well" , "Be successful" , "Grow strongly" , "Develop well" , "Hit rev in order to prosper" .)