Clash is between manager's top and tie (8)
I believe the answer is:
mismatch
'clash' is the definition.
(thesaurus)
'is between manager's top and tie' is the wordplay.
'between' indicates putting letters inside.
'top' suggests taking the first letters.
'and' is a charade indicator (letters next to each other).
'tie' becomes 'match' (I've seen this before).
The initial letter of 'managers' is 'm'.
'm'+'match'='mmatch'
'is' placed inside 'mmatch' is 'MISMATCH'.
(Other definitions for mismatch that I've seen before include "Discrepancy" , "A failure to correspond" , "Unsuitable pairing" , "Inappropriate pairing" , "(Form) unsuitable couple" .)