Small team has a power source (5)
I believe the answer is:
steam
'a power source' is the definition.
(I've seen this in another clue)
'small team' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
's'+'team'='STEAM'
'has' is the link.
(Other definitions for steam that I've seen before include "Source of power" , "fume" , "12 dn water vapour" , "Momentum - boiled water" , "Driving force" .)