Had to avoid bottom in deep end when swimming (6)
I believe the answer is:
needed
'had' is the definition.
('need' can be a synonym of 'have')
'avoid bottom in deep end when swimming' is the wordplay.
I cannot quite see how this works, but
'when' could be 'e' (I've seen this in other clues) and 'e' is found within the answer.
an anagram of 'end' is 'ned' which is within the left over letters.
The remaining letters 'ed' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for needed that I've seen before include "Obligatory" , "Essential; called for" , "Lacked something essential" , "'Lacked, required (6)'" , "Required, necessary" .)