Leaders of swimming team on record pace (4)
I believe the answer is:
step
'pace' is the definition.
(I know that pace can be written as step)
'leaders of swimming team on record' is the wordplay.
'leaders of' indicates taking the first letters.
'on' says to put letters next to each other.
'record' becomes 'EP' (abbreviation for extended play record).
The first letters of 'swimming team' is 'st'.
'st'+'ep'='STEP'
(Other definitions for step that I've seen before include "Rung, dance movement" , "Second half of quick 20?" , "Gradation" , "Footfall" , "Abrupt change; pace" .)