On the other hand, the horse gets in a tangle (4,5)
I believe the answer is:
then again
'on the other hand' is the definition.
(synonyms)
'the horse gets in a tangle' is the wordplay.
'horse' becomes 'nag' (term for an old horse).
'gets' is a charade indicator (letters next to each other).
'tangle' indicates an anagram.
'in'+'a'='ina'
'ina' is an anagram of 'ain'.
'the'+'nag'+'ain'='THEN AGAIN'
(Other definitions for then again that I've seen before include "still" , "however" , "From another point of view" .)