Old lieutenant taking turn to rejoice (5)
I believe the answer is:
exult
'rejoice' is the definition.
(I know that rejoice can be written as exult)
'old lieutenant taking turn' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'lieutenant' becomes 'lt' (abbreviation for lieutenant).
'taking' is an insertion indicator.
'turn' becomes 'u' (a 'U-turn' is a kind of turn).
'ex'+'lt'='exlt'
'exlt' enclosing 'u' is 'EXULT'.
'to' is the link.
(Other definitions for exult that I've seen before include "Be jubilant" , "Show triumphant elation" , "Crow in triumph" , "Rejoice greatly" , "Rejoice intensely" .)