Small and friendly crowd on the move (5)
I believe the answer is:
swarm
'crowd on the move' is the definition.
'swarm' can be an answer for 'crowd' (swarm is a kind of crowd). I'm not certain of the 'on the move' bit.
'small and friendly' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'and' says to put letters next to each other.
'friendly' becomes 'warm' (associated in meaning).
's'+'warm'='SWARM'
Can you help me to learn more?
(Other definitions for swarm that I've seen before include "Large number" , "Find insect population" , "Climb; cluster of bees" , "Horde" , "Moving crowd, of bees say" .)