Suggestion engineers should be brought in by city (6)
I believe the answer is:
breath
'suggestion' is the definition.
(breath is a kind of suggestion)
'engineers should be brought in by city' is the wordplay.
I cannot quite see how this works, but
'engineers' could be 're' (abbreviation for Royal Engineers) and 're' is present in the answer.
'by' could be 'at' and 'at' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for breath that I've seen before include "Air drawn in and expelled out" , "Slight movement of air" , "Respiration" , "Air received and expelled" , "Air in an out of the lungs" .)