A disheartened triallist felt pain in a romantic relationship? (8)
I believe the answer is:
attached
'in a romantic relationship?' is the definition.
(attached to a partner)
'a disheartened triallist felt pain' is the wordplay.
'disheartened' says to hollow out the word (remove centre letters).
'felt pain' becomes 'ached' (I've seen this in another clue).
'triallist' with its centre removed is 'tt'.
'a'+'tt'+'ached'='ATTACHED'
(Other definitions for attached that I've seen before include "Spoken for" , "Joined, connected" , "Fond and affectionate (to)" , "in a relationship" , "Affixed" .)