Horse able to manoeuvre during swim, doing the backstroke? (7)
I believe the answer is:
piebald
'horse' is the definition.
'able to manoeuvre during swim doing the backstroke?' is the wordplay.
'to manoeuvre' is an anagram indicator.
'during' is an insertion indicator.
'swim' becomes 'dip' (dip is a kind of swim).
'doing the backstroke?' says the letters should be written in reverse.
'dip' back-to-front is 'pid'.
'able' is an anagram of 'ebal'.
'ebal' put within 'pid' is 'PIEBALD'.
(Other definitions for piebald that I've seen before include "Two-coloured (horse)" , "(Of horse) patched with two colours" , "Of horse, with patches of white and dark colour" , "Marked in two different colours, especially black and white" , "Bicoloured" .)