Ancient skill in bridge-building (7)
I believe the answer is:
spartan
'ancient skill in bridge-building' is the definition.
I can't tell whether this definition defines the answer.
'ancient skill in bridge' is the wordplay.
'ancient skill' becomes 'art' (I've seen this before. I am not sure about the 'ancient' bit.**).
'in' indicates putting letters inside.
'bridge' becomes 'span' ('span' can be a synonym of 'bridge').
'art' inserted into 'span' is 'SPARTAN'.
Can you help me to learn more?
(Other definitions for spartan that I've seen before include "Indifferent to luxury" , "austere old Greek" , "Frugal" , "Strictly disciplined" , "Rather austere" .)