Second squad’s cool mode of transport (9)
I believe the answer is:
steamship
'mode of transport' is the definition.
'steamship' can be an answer for 'transport' (steamship is a kind of transport). I'm not sure about the 'mode of' bit.
'second squad's cool' is the wordplay.
'second' becomes 's' (common abbreviation).
'squad's' becomes 'team's' ('team' can be a synonym of 'squad').
'cool' becomes 'hip' (hip can mean cool or fashionable).
's'+'teams'+'hip'='STEAMSHIP'
Can you help me to learn more?
(Other definitions for steamship that I've seen before include "Vessel with funnels" , "SS in full" , "I pass them (anag) - vessel" , "What SS stands for" , "Queen Elizabeth, for one?" .)